Wednesday, November 28, 2012

Understanding the Red Sea response to sea level

Fig. 1. Map of Red Sea bathymetry and surrounding topography. Note the small surface area of the Red Sea rainfall catchment marked by the bold dashed line.

This paper describes a novel method to study the sea level record over the last 20 thousand years using Red Sea oxygen isotope records.  The larger scope of the work is described at the University of Southampton Red Sea Project site.

Mark Siddall, David A. Smeed, Christoph Hemleben, Eelco J. Rohling, Ina Schmelzer, William R. Peltier, David A. Smeed, Christoph Hemleben, Eelco J. Rohling, Ina Schmelzer, William R. Peltier
Earth and Planetary Science Letters 225 (2004) 421– 434
(link)

Abstract:  "Here we outline a new, pragmatic methodology to derive relative sea-level estimates from central Red Sea oxygen isotope records based on a previously published model. In this paper, the methodology is described in detail, and it is shown that sealevel change is the dominant factor responsible for the recorded variability in Red Sea delta-O-18 (PDB) for sea level changes greater than 12 m. Variables such as temperature or net evaporation are shown to have relatively small effects on the oxygen isotope record. The modelled delta-O-18 (PDB) to sea level relationship is given in terms of a fifth order polynomial which may be used to describe relative sea level from central Red Sea oxygen isotope records. We show how established sea level records from fossil reef terraces for the last 20 kyr are successfully simulated from central Red Sea oxygen isotope records. We also examine the spatial variability of delta-O-18 (PDB) in the basin over the last 13 kyr."

Wednesday, November 21, 2012

Homo Spiritualis

Traditional people, and I think, the people of the paleolithic, had very probably two concepts which changed our vision of the world.  They are the concept of fluidity and the concept of permeability.  Fluidity means that the contiguities that we have:  man, woman, horse, tree, etc., can shift: a tree may speak, a man can get transformed into an animal and the other way around, given certain circumstances.  The concept of permeability is that there are no barriers, so to speak, between the world where we are and the world of the spirits . . . Humans have been described in many ways, right? and for a while, it was homo sapiens, and it's still homo sapiens:  the man who knows.  I don't think it's good definition at all . . . I would think homo spiritualis.   [From the film Cave of Forgotten Dreams.]

The Elephant in Pre-Colonial Ghana: Cultural and Economic Use Values
Kwame Osei Kwarteng
Journal of Philosophy and Culture, Vol. 3, No. 2 June 2006
(link)

Rites Associated with Elephant Hunting Among the Akan

". . . McCaskie notes that ‘the elephant was both unpredictably dangerous–spiritually as well as physically–and the largest single source of animal food in Asante forest.’[36] This made elephant hunting a perilous venture. The Akan of Ghana have the intrinsic belief that just like mankind, some animals, including the elephant, have spirits which survived the death of the animal. Rattray,[37] Nketia,[38] and Sekyi–Baidoo[39] state that hunters classified wild animals into two: those with spirit (sasammoa) and those without (mmoa). The former were deemed to have malevolent spirits which lived on after the animal had been killed by a hunter, and which could haunt its killer and cause calamity to befall him during subsequent hunting expeditions. Sasamoa include bongo, elephant, roan, waterbuck, duyker, black duyker, yellow–black duyker and antelope. Sekyi–Baidoo points out that, uniquely among these animals, the killing of the elephant reportedly brought honour to the hunter; for this reason, and in spite of the inherent risks, some hunters targeted the elephant, while others avoided it.[40] Clearly, the elephant enjoyed special status among animals with spirit (sasammoa), because it was considered as the king of the jungle. This is illustrated by Akan proverbs such as ‘Ǥsono akyiri nni aboa’ ( there is no wild animal besides elephant), ‘wodi Ǥsono akyiri a hasuo nka wo’ (if you follow the trail of elephant you would not be drenched by dew’etc.)

"Nketia has documented the necessary ritual preparations which fortified elephant hunters spiritually before they embarked on hunting expeditions. This process of fortification involved undergoing a ritual bath.[41]

"In the case of hunters celebrating their first elephant kill, a second ritual called abǤfuo,[42] ‘elephant funeral’, was performed to appease the spirit of the animal.[43] For experienced hunters, abǤfuo was not performed after every kill, since it was assumed that they possessed sufficient spiritual endowment to render them immune to any threat or danger posed by elephant spirits.[44]"

". . . Nketia states that a hunter who killed an elephant plucked a leaf and put it in his mouth and then went home to report the killing, after which he would undergo the necessary ritual bath, which made him acquire physical and spiritual power over animals.[47]

"He suggests that the rationale behind the elaborate ritual was that a hunter was assumed to have died and been resurrected after killing a dangerous animal like an elephant. The occasion was thus both joyous and sobering. The king of all animals, which was thought to have a spirit like a human being, had been killed and this was equated to homicide. Thus while celebrating the elephant kill, cleansing rites needed to be performed to prevent the spirit of the elephant from haunting the hunters.[48] In Kunso, these ‘elephant funeral’ rites commenced at 8.00 pm, and entailed the pouring of libation by the chief hunter to invoke the spirit of dead hunters for their permission and protection against any unforeseen events, which was followed by the singing of hunting songs, drumming and dancing.[49] Failure to appease the spirit of the dead elephant could result in one or another of the following disasters striking the hunter: ‘he would never again be able to kill an elephant; he would grow immensely fat and die; he would always want to sleep; he would eat all day and never be satisfied.’ Rattray explains that these disasters would be caused by the sasa, the spirit of the elephant.[50]"

"While elephant hunting was undoubtedly a hazardous venture, the importance of the elephant and its products in the performance of important social, cultural and economic functions in society meant that hunters risked their lives to hunt the pachyderm."


References:

36. R.S. Rattray, Religion and Art in Ashanti, Oxford University press, Oxford, 1927, p183–184.
37. Nketia, Abofodwom, Ghana Publishing Corp, Accra, 1973, pp7–9.
38. Sekyi–Baidoo, A Study of the Cosmological and Aesthetic Freatures of the Akan Hunters' Song Amoung the People of Kunso, M.Phil Thesis Submitted to the Institute of African Studies, University of Ghana, Legon, 1994, p41.
39. Ibid.
40. Nketia, Abofodwom, op cit, p8.
41. Ibid.
42. Rattray, Religion and Art in Ashanti, , op cit, p184–185, See also Ross, Doran H, ‘More than Meets the Eye: Elephant Memories Among the Akan’ in Elephant : The Animal and Its Ivory in African Culture , Edited Doran H. Ross Hong Kong, Pear River Printing Company, 1992, p 140.
43. Nketia, Abofodwom, op. cit, p8. 44. Sekyi–Baidoo, op cit, p42.
47. Nketia, Abofodwom, op cit, pp8-9.
48. Sekyi–Baidoo, op cit, pp79–100. For full details on the elephant funeral rites read the above pages.
49. Rattray, Religion and Art in Ashanti, op. cit, p184.
50. Nketia, Abofodwom, op. cit, pp8–9.

Tuesday, November 20, 2012

Hidden Markov Model Tutorial on Youtube

Part I

Part II

The Hidden Markov Model Tutorial

A Tutorial on Hidden Markov Models and Selected Applications in Speech Recognition
Lawrence R. Rabiner
(link)

Extension to Hidden Markov Models

"So far we have considered Markov models in which each state corresponded to an observable (physical) event.  This model is too restrictive to be applicable to many problems of interest.  In this section we extend the concept of Markov models to include the case where the observable is a probabilistic function of the state - i.e., the resulting model (which is called a hidden Markov model) is a doubly embedded stochastic process that is not observable (it is hidden), but can only be observed through another set of stochastic processes that produce the sequence of observations."

Natural Selection through the eyes of Information Theory

I'm going to be covering different sections of this fundamental paper piece by piece over the next month or so.  Thanks to the Haldane's Sieve blog for putting it up.  Especially, thanks to the author Steven A. Frank.  I've been stumbling around for almost two years now, knowing the underlying connection between population genetics and communication theory was entropy, but lacking the mathematical formalism to describe the connection.  Interestingly, Frank is at UC Urvine, home of the Henry Samueli School of Engineering.  Here's the intro to the paper:

Natural selection. V. How to read the fundamental equations of evolutionary change in terms of information theory

Steven A. Frank
Journal of Evolutionary Biology
Article first published online: 16 NOV 2012
(link)

Introduction

   "I show that natural selection can be described by the same measure of information that provides the conceptual foundations of physics, statistics and communication. Briefly, the argument runs as follows. The classical models of selection express evolutionary rates in proportion to the variance in fitness. The variance in fitness is equivalent to a symmetric form of the Kullback-Leibler information that the population acquires about the environment through the changes in gene frequency caused by selection.

   "Kullback-Leibler information is closely related to Fisher information, likelihood, and Bayesian updating from statistics, as well as Shannon information and the measures of entropy that arise as the fundamental quantities of communication theory and physics. Thus, the common variances and covariances of evolutionary models are equivalent to the fundamental measures of information that arise in many different fields of study.

   "In Fisher's fundamental theorem of natural selection, the rate of increase in fitness caused by natural selection is equal to the genetic variance in fitness. Equivalently, the rate of increase in fitness is proportional to the amount of information that the population acquires about the environment [2].

   "In my view, information is a primary quantity with intuitive meaning in the study of selection, whereas the genetic variance just happens to be an algebraic equivalence for the measure of information. The history of evolutionary theory has it backwards, using statistical expressions of variances and covariances in place of the equivalent and more meaningful expressions of information. To read the fundamental equations of evolutionary change, one must learn to interpret the standard expressions of variances and covariances as expressions of information."

Monday, November 19, 2012

Woolly Mammoth, Woolly Rhinoceros and Reindeer Lived On Iberian Peninsula 150,000 Years Ago

Spanish researchers found the fossil remains of fauna of glacial climate in 72 Iberian sites,
mostly in the north of the peninsula. (Credit: Peter Novák)

ScienceDaily (Sep. 9, 2010) (Link) — A team made up of members of the University of Oviedo (UO) and the Complutense University of Madrid (UCM) have gathered together all findings of the woolly mammoth, the woolly rhinoceros and the reindeer in the Iberian Peninsula to show that, although in small numbers, these big mammals -- prehistoric indicators of cold climates -- already lived in this territory some 150,000 years ago.

The presence of the woolly mammoth (Mammuthus primigenius), the woolly rhinoceros (Coelodonta antiquitatis), the reindeer (Rangifer tarandus), and to a lesser extent the wolverine (Gulo gulo), the arctic fox (Alopex lagopus), the musk-ox (Ovibos moschatus) and the Saiga antelope (Saiga tatarica), has been linked to the paleoclimatic scale created on the basis of the isotopic composition of oxygen in the ice of Greenland.

"The findings of cold climate fauna in the Iberian Peninsula coincide with the periods of greatest global cooling recorded in the ice of Greenland," Diego Álvarez-Lao, main author of the work and researcher in the Palaeontology Department of the UO explains.

The study, which has been published in the journal Quaternary International, reveals that the oldest remains of mammals adapted to cold climates found in the Iberian Peninsula belong to great prehistoric mammals which lived isolated in Spain 150,000 years ago.

The "glacial fauna" entered the Peninsula at that time because "the environmental conditions in central and northern Europe were so extreme that the animals were obliged to migrate to the south, where the climate was less severe," Álvarez-Lao explains.

Thursday, November 15, 2012

Multipath

Multipath signalling in a communication system is a propagation phenomenon where a signal propagates by multiple paths from sender to receiver.  As the signal travels through the media in each path, it experiences destructive and constructive interference and phase shifting.

Successfully communicated multipath signals at the receiver are usually redundant.  If not, they would likely not survive negative impacts of multipath such as fading and could not be reconstructed into a comprehensible format at the receiver.

A possible analogy in population genetics can be drawn when a population splits into two or more separated, isolated populations.  Over time, these separated populations undergo positive and negative selection as well as diffusion.  When the separated populations encounter each other again, and are measured, it is possible to misinterpret the underlying structure of the reconstructed population if the measurement system cannot model multipath effects.

Another analogy can be drawn with respect to redundancy.  The genome seems to have high redundancy.  Recent examples of this are the finding of the development of lactase persistence in Europeans and East Africans and the development of high altitude adaptation in Tibetans and Ethiopians on different loci.

(Update November 19th:  It occured to me that some might take this communication system analogy as an argument for intelligent design.  The analogy is not meant as an argument for Intelligent Design. Rather, it is meant to suggest that some ideas from formal communication theory may be illustrative in population genetics.  I mentioned the seminal communication theory paper by Claude Shannon in the last post, MULTIMIX.  Here's the link again:  A Mathematical Theory of Communication, Claude Shannon, The Bell System Technical Journal, 1948.)


Related papers:

The genetic architecture of adaptations to high altitude in Ethiopia
Alkorta-Aranburu et al.
preprint
http://arxiv.org/abs/1211.3053

The Origins of Lactase Persistence in Europe
Yuval Itan et al.
PLoS Comput Biol 5(8): e1000491. doi:10.1371/journal.pcbi.1000491
(link)

Genetic Evidence for High-Altitude Adaptation in Tibet
Tatum S. Simonson et al.
Science Vol. 329. no. 5987, pp. 75 - 78
DOI: 10.1126/science.1190371
(link)

Convergent adaptation of lactase persistence in Africa and Europe
Tishkoff et al.
Nature Genetics 39, 31 - 40 (2007)
Published online: 10 December 2006 | doi:10.1038/ng1946
(link)

Wednesday, November 14, 2012

On "[ ] is a complex disease"

Anne Buchanan writes a super post about reality in genetic and genomic research.  (link)

Thank you.

MULTIMIX

Introduction:
(link)

MULTIMIX is a program that fits a statistical model to linked genome-wide SNP data from admixed individuals to learn about their ancestral origins. It is applied to a dense set of biallelic SNPs and will estimate the ancestral population of origin at each SNP - the local ancestry.

To infer the population of origin at each locus along the admixed chromosome MULTIMIX uses panels of either phased haplotypes or unphased genotypes sampled from each of the candidate ancestral population. The MULTIMIX model is applicable to any number of ancestral source populations, as well as any combination of phased or unphased admixed samples and source panel data.

The user has a choice of three statistical methods with which to implement the model : MCMC sampling, the EM algorithm or the Classification-EM (CEM) algorithm. Each of these methods makes inference on the local ancestry at windows of SNPs meaning that the sites of switches in ancestry are restricted to occur only at the boundaries between these windows. To refine the estimate on the location of switches, an additional step to resolve the boundaries between chunks of differing ancestry can be implemented.

The paper:

Claire Churchhouse, Jonathan Marchini
Genetic Epidemiology
7 Nov 2012
DOI: 10.1002/gepi.21692
(link)

Abstract:  "We describe a novel method for inferring the local ancestry of admixed individuals from dense genome-wide single nucleotide polymorphism data. The method, called MULTIMIX, allows multiple source populations, models population linkage disequilibrium between markers and is applicable to datasets in which the sample and source populations are either phased or unphased. The model is based upon a hidden Markov model of switches in ancestry between consecutive windows of loci. We model the observed haplotypes within each window using a multivariate normal distribution with parameters estimated from the ancestral panels. We present three methods to fit the model—Markov chain Monte Carlo sampling, the Expectation Maximization algorithm, and a Classification Expectation Maximization algorithm. The performance of our method on individuals simulated to be admixed with European and West African ancestry shows it to be comparable to HAPMIX, the ancestry calls of the two methods agreeing at 99.26% of loci across the three parameter groups. In addition to it being faster than HAPMIX, it is also found to perform well over a range of extent of admixture in a simulation involving three ancestral populations. In an analysis of real data, we estimate the contribution of European, West African and Native American ancestry to each locus in the Mexican samples of HapMap, giving estimates of ancestral proportions that are consistent with those previously reported."


Related paper:

A Mathematical Theory of Communication
Claude Shannon
The Bell System Technical Journal
Vol. XXVII, No. 3, July 1948
(link)

Dagomba


This is an excerpt of some field recordings which were recorded by Nana Kimati Dinizulu in the Northern Region of Ghana, West Africa. [The Dagomba people inhabit the northern savannah of Ghana.] The music featured in this segment is performed by Fusani Tia on Jenjeli, which is a one string instrument of the Dagomba people and his son Muhammad Kusani who plays Denkenkelen, an idiophone made of iron. This is an ancient form of music that is now played by few musicians.

Hunting Elephants: From the Earliest Times . . .

The Elephant in Pre-Colonial Ghana: Cultural and Economic Use Values
Kwame Osei Kwarteng Journal of Philosophy and Culture, Vol. 3, No. 2
June 2006
(link)

"From the Earliest Times"

". . . according to Nketia, before the advent of the cash crop economy, not only was hunting the most important profession in Ghana, it also required bravery and a thorough knowledge of the forest. Nketia categorises hunters into assistant hunters and master hunters. The distinction between the two was based on the type of animal hunted. Assistant hunters killed only small animals, while master hunters killed dangerous animals like elephants and buffaloes. Master hunters were also ranked according to their exploits, chiefly the number of elephants that they killed during their career. Accordingly, there were three distinct ranks of master hunter: the lowest on the rung were hunters who had killed only one elephant; occupying an intermediate rank were those who had killed two elephants; while those who killed three or more elephants in their career as hunters were ranked highest. [1]"

"What were the likely origins of hunting in Ghana? Evidence gleaned from archaeology, and corroborated by oral tradition, provides some answers. According to Anquandah, recent archaeological studies carried out in the woodland savannah and forest belts of Ghana have revealed that from about 10,000 B.C. onward, Late Stone Age hunter–gatherers who fashioned microlithic and flake industries occupied the savannah and forest, and set up intensive food gathering, fishing and hunting economies [2] . . ."

"The archaeological evidence suggests further that Early and Later Stone Age populations were culturally adapted to their specific ecological zones. For example, a microlithic population represented at Gao lagoon in the Accra plains combined hunting with exploitation of shellfish and other fish resources in the local lagoon and river environment. On the other hand, the populations of the savannah zone of Ghana had a strong microlithic tradition which exploited the animal resources of that ecological belt. However, in the forest zone, opportunities for hunting were minimal, with people specialising in grubbing up wild tubers and roots using stone picks and hoes[3] . . ."

"What were the hunting methods employed by the ancient hunters? This may be inferred by examining the various hunting methods known to have been employed in various African cultures which were contemporaneous with the period we are considering. Van Couvering identifies some hunting tactics employed by modern African hunters which were also used by ancient hunters as mob attacks with spears; pitfalls; burning of game–rich bush; and hamstringing.[4]"

"It is reasonable to suppose that of these techniques, the ancient elephant hunters in Ghana during the Late Stone Age used either bush burning or hamstringing, although Van Couvering admits that the latter ‘entailed a high risk on the part of a hunter equipped only with a stone axe or knife’[5]"

"During the Iron Age both the Akan in the forest belt adn savannah groups like the Gonja and Mole-Dagbani used bows and arrows, spears and javelins as traditional weapons for war as well as for hunting purposes. However, from the 1650s, European trading companies introduced firearms into the Gold Coast with the result that arms proliferated in the coastal and forest regions and were used for military and hunting purposes. The adoption of muzzle–loading guns to hunt elephant and other game led to the emergence of two distinct elephant hunting methods in the country. Coastal groups, along with the Akan who lived in the forest belt (Asante, Assin, Denkyira, Kwahu, Akwamu, Akyem, etc), where European goods circulated freely, bought these guns and used them, both for defensive and offensive purposes, and for hunting elephants and other animals. At the same time, savannah inhabitants continued to use their traditional bows, arrows and spears for elephant hunting. Arhin indicates that arms and ammunition became available in the northern markets after 1874, when Asante authority over her hinterland was undermined by the British invasion of Kumasi. It appears that long after Asante had stopped restricting movement of arms and ammunition to the north, savannah elephant hunters continued to use bows, arrows and spears. This is borne out by Cardinall, a former District Commissioner of Northern Territories and Western Ashanti who notes in In Ashanti and Beyond that the north had practically no guns in the early twentieth century, and thatelephants were killed with bows, arrows and spears.[6]"

"There is reason to believe, too, that both the Ntereso and Kintampo areas have a long tradition of hunting and history of large elephant populations. Indeed elephant hunting here, which started in pre–historic times, appears to have persisted into the twentieth century. In the case of Kintampo, hunting traditions recorded by Sekyi–Baidoo indicate that local towns and villages, and adjacent districts in the northern part of Brong Ahafo Region, particularly towns like Kunso, Dromankese, Krabonso, Tanoboase, Tuobodom, Nchiraa and Droboso, were noted for elephant hunting until the disappearance of elephants from these areas.[7] Traditions related by Nana Kwabena Bofuo, a renowned elephant hunter and the Chief Hunter of Kunso and Nana Kwame Ntem, a hunter and Atufuohene of Abease traditional area, confirm the abundance of elephants in the the Nkoranza, Kintampo and adjoining districts up to the Afram plains . . ."

"With respect to Ntereso in northern Ghana, there is evidence which suggests that the area’s long tradition and history of elephant hunting was due to the area’s rich elephant resources which might date to antiquity. Daaku writes, for instance, that Gonja and Dagomba in northern Ghana were major sources of Asante ivory supplies in pre–colonial times, notably when the two areas were under the hegemony of Asante. Also, during the colonial era, elephant hunting was prevalent in the north, particularly in Gonja district. For instance, in 1924 the Chief Commissioner of the Northern Territory in a report referred to the invasion of then Bole District by Asante hunters, providing confirmation that elephant hunting was still taking place in the first half of the twentieth century in Ntereso."

References

[1] James Anquandah, Rediscovering Ghana's Past, Longman, Essex, p. 53.

[2] Rattray, Ashanti Law and Constitution,op cit, p. 218, the exact time Rattray is referring to is not known, but probably he is referring to the period before the introduction of guns into the country in the 17th Century.

[3] Ibid, p. 54.

[4] John A. Van Couvering, ‘Proboscineans, Hominids, and Prehistory’ in Elephant: The Animal and Its Ivory in African Culture, Ed. Doran H. Ross, Pear River, Hong Kong, 1992, p75.

[5] A.W. Cardinall, In Ashanti and Beyond, Johnson Print Corporation, London, 1971, p167.

[6] Sekyi–Baidoo, A Study of The Cosmological and Aesthetic Features of the Akan Hunters’ Song Among the People of Kunso, M.Phil Thesis Submitted to Institute of African Studies, University of Ghana, Legon, 1994, p. 30.

[7] Interview with Nana Kwabena Bofuo, Chief Elephant Hunter, 80 years old Kunso, 24/01/06.

Tuesday, November 13, 2012

The Transitional Humans

A nice introduction to early transitional humansHomo erectus, Neandertals and Glacial Cycles has been put up by Dr. Dennis O'Neil, a behavioral scientist at Palomar College, San Marcos, California. (link)

Dynamics of genetic and morphological variability within Neandertals

John Hawks
Journal of Anthropological Sciences Vol. 90 (2012), pp. 1-17
2012
(link)

I got around to reading John Hawks' paper which I thought would be a summary paper of current work on Neandertals.  While it is a summary paper, I found it to be the most riveting description of Neandertal behavior I have ever read.  You probably want to read the entire paper.  I started excerpting the paper but ended up copying about a third of it here.  The paper is highly relevant to the model of a refugia and range shift model for human origins.

Neandertal variation and "varieties"

"Southwest Asian Neandertals"

"This group included the entire known fossil record of the Levant to the Zagros, including Skhul, Tabun, Zuttiyeh, and Qafzeh (all in the Levant) and Shanidar, Iraq.  Howell [1957] noted the divergent opinions of anthropologists about the evolutionary scenario that generated this sample.  He offered the opinion that the Tabun had affinities with Early Neandertal people, and that the region had undergone a trend of "sapiensization" explaining the Skhul sample."

"Howell identified these varieties of Neandertals to clarify his position on the Neandertal ancestry of recent humans.  In his view, several previous authors had been too categorical in their insistence that Neandertals could not have been ancestors of modern peoples.  He allowed that the classic Neandertals may have been too specialized to have given rise to later populations within Europe.  But the early Neandertals were less anatomically specialized and may have been ancestral to modern humans in some other, non-European, region.  Moreover, the Southwest Asian Neandertals appeared to provide evidence of an evolutionary trend toward modern humans."

Emerging problems with Neandertal varieties

"Several workers after Howell added the concept of a north-south axis of Neandertal diversification within Europe.  Rosas and colleagues (2006) noted that southern Neandertals tend to have increased heights of the lower face and broader faces than the northern sample of Neandertals within Europe."

"Mitochondrial DNA"

"The pattern of mtDNA evolution within Neandertals suggests that repeated turnover of the population of European Neandertals did happen.  When considering the entire sample of mtDNA, the amount of variation within the Neandertal sample is approximately equal to the variation within living people across the same geographic range, from Spain to Central Asia (Caramelli et al., 2008, Krause et al., 2007).  The common ancestor of all Neandertal mtDNA sequences lived approximately 200,000 years ago, around the same time as the modern human mtDNA last common ancestor (Dalen et al., 2012).   Taken by themselves, these comparisons are consistent with the hypothesis that Neandertals had approximately the same population structure and demographic history as modern Eurasians.  However, when we compare earlier and later Neandertals, the picture is more complex.  The sample of Neandertal mtDNA taken from European specimens after 50,000 years ago is depauperate in variation compared to the full sample (Lalueza-Fox et al. 2008).  The lack of variation in later European Neandertals is not consistent with these being a sample drawn from a small geographic area of a large distribution, without demographic turnover (Dalen et al., 2012.)  Instead, it appears that the western part of the Neandertal range underwent at least one episode of large-scale migration and partial population replacement.  A tightly related clade of sequences includes the specimens from Vindija, El Sidron and Feldhofer, seven specimens in all.  These are among the latest Neandertals in the west.  The Central Asian or eastern European portion of the Neandertal range retained greater mtDNA variation in this later time period, possibly indicating that this area was a source for later Neandertals in Western Europe . . ."

"Fabre and colleagues (2009) also emphasized a biogeographic division of mtDNA into easter and western groups.  They used a different methodology, focused upon whether the geographic range of Neandertals could be divided into replicable subsamples.  In addition to the division into Central Asian and European groups, the study also suggested that the Italian and Croatian specimens might belong to a "southern" group.  This study did not consider the times represented by different sites, and adding the dynamic reflected by time would likely change the groupings.  By testing a priori models, the study avoided some of the problems attendant upon the tree-based approaches described above."

"Nuclear DNA"

"Three Neandertals from Vindija have been represented by substantial sequencing of the nuclear genome, averaging nearly 1x coverage for each of them.  Much smaller fractions of the nuclear genome have been recovered from Neanderthal specimens from Feldhofer Cave, El Sidron, and Mezmaiskaya (Green et al., 2010).  All of these except for Mezmaiskaya are among the group of later Western European Neandertals discussed above, all of which fall intoa single mtDNA clade.  This is therefore a highly constrained set of Neandertals in space and time.   The full set of mtDNA extends includes an eastern range with greater diversity and much earlier specimens in Western Europe."

"The most celebrated result from the nuclear DNA evidence is the finding that non-Africa populations today derive a proportion of their ancestry from Neandertals (Green et al., 2010).  The fraction of ancestry represented by such introgression form Neandertals is between 1 and 4 percent of the genealogical ancestry of individuals with European, Asian or other non-African origins.  Some of the similarity of non-Africans to Neandertals may be attributable to the ancient Middle Pleistocene structure of African populations (Eriksson & Manica, 2012), but this effect alone cannot explain the pattern of similarities, which therefore require substantial introgression (Yang et al., 2012).  It is possible that some similarities of living people and Neandertals resulted from gene flow between Neandertals and African contemporaries before the Late Pleistocene dispersal of modern populations . . ."

Reconciling paleogenomics and morphology

". . . Two avenues of evidence will provide more insights about Neandertal population dynamics.  Obviously, uncovering more nuclear genomes from Neandertals or early Upper Paleolithic humans would advance our knowledge greatly.  Tempering this expectation is that the later western Neandertals, with lower genetic diversity, are the ones most likely to provide more genetic data.  Earlier Neandertals, and the Neandertals from central Asia, would be most useful to uncover new knowledge about the population dynamics of this ancient group. A second source of evidence may come from the introgression of Neandertal genes into later human populations.  As we begin to uncover the genes of living people that came from Neandertals, we face the possibility that these genes may represent different ancient Neandertal groups to greater or lesser degrees.  The initial work on Neandertal genetics suggested that most of the population mixture with Neandertals may have happened in west Asia (Green et al., 2010).  That would suggest that European Neandertals are themselves somewhat genetically distinct from the population that gave rise to most Neandertal genes in recent populations.  Comparing different Neandertals with each other will help us uncover the structure of the population that gave rise to Neandertal ancestry in living people . . ."

Population dynamics

" . . . The attention to "early" Neandertals as a group dating to the last interglacial brought with it the understanding that Neandertals had persisted through at least one entire glacial cycle.  Howell (1952) proposed that glacial cycles provided the isolation that enabled classic Neandertals to evolve their specialized anatomy.  Weckler (1954) argued that isolation was one consequence of glaciations, but that long-distance migrations and recolonizations of formerly periglacial habitat was an important cause of population change in Neandertals and the modern humans who encountered them."

"Today, our knowledge of the geographic range of Neandertals confirms their existence across a broad range of climate regimes.  From the Altai to Spain, the known geographic range of Neandertals covered more than 7000 kilometers east to west.  On the longitudinal range is little doubt, because of the mtDNA evidence European Neandertal specimens to Okladnikov Cave (Krause et al., 2007).  Okladnikov is at present the easternmost site to produce skeletal remains attributable to Neandertals, although other sites with similar archaeology are found in the Altai.  The Neandertals also covered a substantial range in latitude.  The northernmost Neandertal site may be Byzovaya, which does not present skeletal remains but does include a Late Mousterian assemblage with some technical links to central European Neandertal sites (Slimak et al., 2011) . . . Although the European climatic conditions oscillated considerably during the Late Pleistocene, the Neandertals seem likely to have been capable of adapting to change conditions, either by tracking ecotones as climate shifted or by changing their subsistence strategies to meet new requirements.  In other words, the archaeological record by itself is sufficient to show us that Neandertal populations were highly dynamic in areas where habitation was possible only during intermittent climatic periods."

"Archaeological evidence along gives us some indications that Neandertals rapidly colonized new regions when they became suitable for habitation.  The possible excursion of Late Mousterian people north of the Arctic Circle to Byzyvaya and Mamontovaya Kurya are strong indicators of such potential, if these sites truly represent Neandertal activity.  Bar-Yosef (1992) suggested that later Neandertal sites in the Levant, including Amud and Kebara, may represent the recolonization of this area from Europe as cold conditions intensified during the Wurm glaciation.  Shea (2008) considered the record of modern and Neandertal activity in the Levant to represent multiple cases of population turnover, as climate shifts caused successive populations of Paleolithic humans to abandon the area or become locally extinct."

"Across northwestern Europe, from Britain to Poland, an area of more than a million square kilometers was abandoned by Neandertals during the early stages of the last glaciation and not reinhabited until after approximately 60,000 years ago.  The intermittent occupation of these parts of Europe was likely not a function of "habitat tracking" by Neandertals, but instead a record of regional expansions and partial extinctions when climatic conditions deteriorated (Hublin & Roebroeks, 2009).  White & Pettitt (2011) suggested a very small Neandertal population size in northwestern Europe during the late Middle Paleolithic, and considered the possibility that the occupation of Britain was maintained as seasonal hunting camps rather than permanent settlements.  This kind of occupation would put movements of several hundred kilometers into the ordinary behavior pattern of individual Neandertals.  At an extreme, the survival of Neandertals on the northwestern tier of Europe may have been precarious (White, 2006).  From the perspective of population dynamics, this does not suggest a dense, stable population, but instead one of great mobility and repeated ability to colonize and exploit new opportunities . . ."

Sunday, November 11, 2012

"Refugia and Range Shifts Model" and the Origin of Modern Humans

I've added a side bar on the right for the posts on this blog that together construct a picture of the "Refugia and Range Shifts Model" for the origin of modern humans as an interaction between Eurasian and African refuges due to climate change induced by glacial cycles during the Quaternary.

Thursday, November 8, 2012

Molecular Dissection of the Basal Clades in the Human Y Chromosome Phylogenetic Tree

Rosaria Scozzari, Andrea Massaia, Eugenia D’Atanasio, Natalie M. Myres, Ugo A. Perego, Beniamino Trombetta, Fulvio Cruciani
PLOS ONE, November 2012
(Open Access link)

Published today is a new paper on an updated y-chromosome phylogeny.  Dienekes has kindly put the phylogeny and abstract online, so I won't recopy them here. 

The most significant finding of the paper is the connection of four A1b y-chromosomes, the deepest phylogeny in the tree, to two men from Ghana, one man in Cameroon and one in Algeria: "Two A1b chromosomes from a previous work (one from Algeria and one from Cameroon) [16] were included in this study together with two newly identified A1b chromosomes, whose geographic origin can be traced back to west-central Africa (Ghana) on the basis of the microsatellite profile (data not shown). It is worth noting that three additional A1b chromosomes have been recently found in Caribbean populations, which exhibit substantial Y-STR haplotype sharing with Y chromosomes from Gabon [35], [36]. Taken together, all these data reinforce the hypothesis of an origin in the north-western quadrant of the African continent for the A1b haplogroup [16], and, together with recent findings of ancient Y-lineages in central-western Africa [19], provide new evidence regarding the geographical origin of human MSY diversity."

A second finding is the identification of "a chromosome from southern Europe as a new deep branch within haplogroup C (C-V20 or C7, Figure S1). Previously, only a few examples of C chromosomes (only defined by the marker RPS4Y711) had been found in southern Europe [32], [33]. To improve our knowledge regarding the distribution of haplogroup C in Europe, we surveyed 1965 European subjects for the mutation RPS4Y711 and identified one additional haplogroup C chromosome from southern Europe, which has also been classified as C7 (data not shown). Further studies are needed to establish whether C7 chromosomes are the relics of an ancient European gene pool or the signal of a recent geographical spread from Asia." 

The paper also includes better definition of other aspects of the A and B y-chromosomes as well as some important additions to the basal F y-chromosome.

It's great to see more in depth attention paid to the genetics of West Africa and also nice to see Italy considered both as a refuge and as a potential path for Out of Africa expansions.

Related:

News Flash:  Developments with Y Haplogroup A (link)

For those of you new to this blog, in the right hand side bar under "WEST AFRICA", there is a list of the posts covering culture, language, geography and genetics of West Africa.

Wednesday, November 7, 2012

The Date of Interbreeding between Neandertals and Modern Humans

Sriram Sankararaman, Nick Patterson, Heng Li, Svante Pääbo, David Reich
PLOS Genetics, October 2012
(link)

This paper evaluates various models of divergence between Africans, Europeans and Neandertals.  Hybrid model (e) of the paper, shown in Figure 2, below, is most closely akin to the human version of the "refugia and range shifts model" of the Marbled White butterfly.  In one possible scenario of this model, the first branch occurs when Africans diverge from Neandertals during the Holstein interglacial (Timeline of glaciation).  Then early Scladina-like Neandertals admix back with Africans, possibly in Iberia or Morocco, 150 kya when the sea level is low enough to make it more likely.  As the sea level rises, the Scladina Neandertal-Africans on the European side are cut off in an increasingly icy domain.  The Scladina Neandertal-Africans in Morocco thrive.  Their descendants marry Africans who have little or no Scladina ancestry.  At about 50 kya, the Scladina Neandertals who are cutoff in Western Europe are replaced by the Vindija like Neandertals. Shortly thereafter, Africans with perhaps a remnant of Scladina Neandertal admixture arrive once again in Europe. Occasionally, they have children with the Vindija Neandertals.  All of the Neandertals, Vindija in Europe and Scladina in Africa, are eventually absorbed into the dominant population of homo sapiens from Africa . . .
Figure 2.  Classes of demographic models relating Africans (Y), Europeans (E), and Neandertals (N).  a) Recent gene flow but no ancient structure. RGF I has no bottleneck in E. RGF II has a bottleneck in E after gene flow while RGF VI has a bottleneck in E before the gene flow. RGF IV and V have constant population sizes of Ne = 5000 and Ne = 50000 respectively. b) Ancient structure but no recent gene flow. AS I has a constant population size while AS II has a recent bottleneck in E. c) Neither ancient structure nor recent gene flow. NGF I has a constant population size while NGF II has a recent bottleneck in E. d),e) Ancient structure+Recent gene flow. HM IV consists of continuous migration in the Y-E ancestor and the Y-E-N ancestor while HM I consists of continuous migration only in the Y-E ancestor. HM II consist of a single admixture event in the ancestor of E while HM III also models a small population size in one of the admixing populations.

Further comments (November 8th):  In reality, there is very strong evidence based on Y-chromosome and mtDNA, that for many if not most populations, Hybrid model (e) is incomplete.  There are subsequent events, such as the migration of the carriers of the E y-chromosome into Europe, some time since the last ice age and before the Holocene Climatic Optimum.  Carriers of the R-V88 y-chromosome and H1 mitochondrial DNA make their appearance in North Africa over the same time frame.  Therefore, a hybrid model for the interaction of populations between Europe and Africa up to the Holocene Climatic Optimum demands allowance for at least four major admixing events: (1) Scladina-like Neandertals with Africans approximately 150kya, (2) Vindija-like Neandertals with Europeans in the window suggested in the above paper, (3) Europeans with North Africans during the last ice age, and (4) North Africans with Europeans during the last ice age. Further complicating the picture are the layers due to recent demographic events of the Holocene Climatic Optimum and the last several thousand years.  This already complex model doesn't even begin to touch upon the migrations to Asia, Southwest Asia and the Americas.  Drift, diffusion, isolation, migration and selection are always at work.  It is therefore not surprising that finding the genetic signature to prove this complex model is very difficult.

Mousterian at Jebel Irhoud: Wherefore Art Thou?

O Romeo, Romeo! wherefore art thou Romeo?
Deny thy father and refuse thy name;
Or, if thou wilt not, be but sworn my love,
And I'll no longer be a Capulet.


So then, what is the timing of our Neandertal and Homo sapien Romeos and Juliets?  How many times and when do they meet in North Africa?  In Europe?  I've put together all the quotes, diagrams, and references I believe are contributing to my current thinking on this topic.  I hope that all the children of the Montagues and Capulets can learn to get along on this fragile planet.


Neanderthal extinction as part of the faunal change in Europe during Oxygen Isotope Stage 3
John R. Stewart
Acta Zoologica Cracoviensa - Series A: Vertebrata, Vol. 50, Numbers 1-2, May 2007, pp. 93-124(32)
(link)

"The cold-adapted mammals as a whole, such as the extinct mammoth and extant species like the reindeer and arctic fox, did not retreat from the north as the climate cooled like the Neanderthals."

"... Neaderthals were presumably a warmer-continental adapted species, based on their geographical distribution through time.  Neanderthals seem to have been better-suited to the Mediterranean during the Late Pleistocene than to the more northern parts of Europe."


Partial Genetic Turnover in Neanderthals:  Continuity in the East and Population Replacement in the West
Dalen et al
Molecular Biology and Evolution (2012) 29 (8): 1893-1897
(link)


"Our analyses indicate that recent western European neandertals (<48 kyr) constitute a tightly defined group with low mitochondrial genetic variation in comparison with both eastern and older (>48 kyr) European neandertals. Using control region sequences, Bayesian demographic simulations provide higher support for a model of population fragmentation followed by separate demographic trajectories in subpopulations over a null model of a single stable population. The most parsimonious explanation for these results is that of a population turnover in western Europe during early Marine Isotope Stage 3, predating the arrival of anatomically modern humans in the region."


The Neanderthal Genome
Science Online Magazine
(link)

Figure from the Neanderthal Genome article:  "At home in Eurasia"

Marnie'e note:  With regard to the southern extent of the Neandertal range, this map may need a little refinement.


References:


Related Posts on this blog:

The Who and When of the Neanderthal Survivors (link)

Ancient Crossings (link)


Related Posts on John Hawks' blog:

Taking the mtDNA pulse of Neandertal populations (link)

Which population in the 1000 Genomes Project samples has the most Neandertal similarity? (link)


Related Media, Ethnomusicology and Archaeological Research:

Grotte Scladina:  Un patrimoine archéologique exceptionnel à découvrir absolument (link)

Cave of Forgotten Dreams [Werner Herzog film about the archaeological research at the Chauvet Cave] (link)

Fliegel Jezerniczky EXPEDITIONS [Rock Art Expeditions and rock art archaeological research] (link)

Vintage Palmwine
Daniel Amponsah[Koo Nimo], Thomas Osai Ampoumah [T. O. Jazz], Kwaa Mensah
Highlife recorded in Ghana in the Bokoor Studios, Ghana
John Collins Recording
2003 Otrabanda Records & Music Distributor (link)
From Amazon (link)


Additional Related Papers and References:

North African genetics through the prism of ADMIXTURE
Luis Aldamiz
Dec, 2011
(link)

The Archaeology of Africa:  Food, Metals and Towns (One World Archaeology)
Bassey Andah (Editor), Alex Okpoko (Editor), Thurstan Shaw (Editor) and Paul Sinclair (Editor)
1995

A Coperican Reassessment of the Human Mitochondrial DNA Tree from its Root
Behar et al
The American Journal of Human Genetics, Volume 90, Issue 4, 675-684, 6 April 2012
(link)

The Identity and Timing of the Aterian in Morocco
A. Bouzouggar and R. N. E. Barton
in Modern Origins:  A North African Perspective, Chapter 7
Jean-Jacques Hublin and Shannon P. McPherron, Editors
Springer, 2012

Tracing Past Human Male Movements in Northern/Eastern Africa and Western Eurasia:  New Clues from Y-Chromosomal Haplogroups E-M78 and J-M12
Cruciani et al
Mol Biol Evol24 (6): 1300-1311. doi: 10.1093/molbev/msm049


Ancient watercourses and biogeography of the Sahara explain the peopling of the desert
Drake et al
PNAS 2010
(link)

The Civilizations of Africa:  A History to 1800
Christopher Ehret
University of Virginia Press
2002

mtDNA Diversity of Ghana:  a forensic and phylogeographic view
Liane Fendt, Alexander Roeck, Bettina Zimmerman, Martin Bodner, Thorsten Thye, Frank Tschentscher, Ellis Owusu-Dabo, Tanya M. K. Goebel, Peter M Schneider, Walther Parson
Forensic Science International: Genetics
2012
(link)

Y-Chromosomal Variation in Sub-Saharan Africa:  Insights Into the History of Niger-Congo Groups
de Filippo et al.
Oxford Journals
(link)

Refining the eustatic sea-level curve since the Last Glacial Maximum using far- and intermediate-field sites
Fleming et al
Earth and Planetary Science Letters 163 (1998) 327-342
(link)

Fliegel Jezerniczky EXPEDITIONS
(Rock Art Expeditions and Web Site)
(link)

The Messak Project and Natural Preservation and Sustainable Tourism (south-western Libya)
Gallinaro et al
Antiquity  Volume 086 Issue 331 March 2012
(link)

Modern Human Desert Adaptations:  A Libyan Perspective on the Aterian Complex
E. A. A. Garcea
in Modern Origins:  A North African Perspective, Chapter 9
Jean-Jacques Hublin and Shannon P. McPherron, Editors
Springer, 2012

A Draft Sequence of the Neandertal Genome
Green et al
Science 7 May 2010:
Vol. 328 no. 5979 pp. 710-722
DOI: 10.1126/science.1188021
(link)

From Africa to Europe and back:  refugia and range shifts cause high genetic differentiation in the Marbled White butterfly Melanargia galathea
Jan C Habel, Luc Lens, Dennis Roedder and Thomas Schmitt
BMC Evolutionary Biology 2011, 11:215
(link)

Comparative phylogeography of African savannah ungulates
E. D. Lorenzen, R. Heller, H. R. Siegismund
Molecular Ecology, Volume 21, Issue 15, pages 3656-3670, August 2012
(link)

Hunter-Gatherer Foraging Strategies in Tropical Grasslands:  Model Building and Testing in the East African Middle and Later Stone Age
Curtis W. Marean
Journal of Anthropological Archaeology 16, 189-225 (1997)
(link)

The genetic prehistory of southern Africa
Pickrell et al
Preprint
(link)

A propos de quelques gravures rupestres de l'Ajal
Jean-Loïc Le Quellec
Persée, Bulletin de la Société préhistorique française, 1993, vol. 90, issue 5, pp. 368-376.
(link)

North African Populations Carry the Signature of Admixture with Neanderthals
Sánchez-Quinto et al
PLOS ONE, 2012
(link)

Spatial and Temporal Variation in the Nature of Pleistocene Pluvial Phase Environments Across North Africa
J. R. Smith
in Modern Origins:  A North African Perspective, Chapter 3
Jean-Jacques Hublin and Shannon P. McPherron, Editors
Springer, 2012

The genetic structure and history of Africans and African Americans
Tishkoff et al
Science, 2009
(link)

Monday, November 5, 2012

From Africa to Europe and back: refugia and range shifts cause high genetic differentiation in the Marbled White butterfly Melanargia galathea



Jan C Habel, Luc LensDennis Rödder and Thomas Schmitt
BMC Evolutionary Biology 2011, 11:215
(Link)

"To study the biogeographical importance of the Maghreb region and its connection with Europe, we selected the Marbled White butterfly species complex Melanargia galathea (Linnaeus, 1758) and Melanargia lachesis (Hübner, 1790) as a model system using two analytical tools (allozyme polymorphisms and distribution modelling).  Today, M. galathea is widely distributed from the Maghreb region (mountain ranges of Morocco, Algeria and Tunisia)[22,23] to the English Midlands [24], and from the Pyrenees[25] to the Baltic Sea in Poland [26]. On the Iberian Peninsula, M. galathea is replaced by its sibling species M. lachesis. Thus, the Italian peninsula is the only possible link between North Africa and Europe for M. galathea."

"A neighbour joining phenogram based on allele frequencies (Figure 1) showed a first split between M. galathea and M. lachesis with a genetic distance [28] of about 0.9. The second split between M. galathea populations from Tunisia and Sicily on the one hand and all remaining M. galathea populations on the other was in average about half of the genetic distance of the first split. The outgroup M. lachesis routing the tree also supports this split being the first one in M. galathea. The Tunisia - Sicily group showed a further genetic differentiation between these two geographic regions. All these splits are supported by bootstrap values. The remaining populations split into five groups, the populations from Morocco and four European groups: (i) mainland Italy and southern France (Condat), (ii) western Balkans and western Carpathian Basin, (iii) eastern Balkans, Romania and Central Europe, as well as (iv) south-western Alps (Col de Tende)."

Figure 2.  Individual based genetic classification of Melanargia galathea and M. lachesis.  Bayesian analysis of all M. galathea and M. Lachesis populations performed using the STRUCTURE software.  Analyses for K = 2 to K = 8 are depicted. 

"STRUCTURE plots (for K = 2 to K = 8) support the topology of the neighbor joining phenogram (Figure 2); the sequence of splits of STRUCTURE groups is mostly reflecting the genetic distances in the tree. Additionally, the samples from Morocco are consistently separated as one group from all other M. galathea populations from K = 5 onwards."

"Thus, these analyses strongly support (i) the genetic break in the Maghreb, (ii) the break between Sicily and mainland Italy, (iii) the differentiation into four genetic lineages in continental Europe, (iv) the cohesiveness between Sicily and Tunisia, (v) the lack of differentiation from the eastern Balkans via Romania to Central Europe and (vi) the strong genetic similarity between mainland Italy and southern France."

Figure 4.  Biogeographic scenario of Melanargia galathea and M. lachesis. Range expansions and retractions of M. galathea and M. lachesis (on the Iberian Peninsula) during the past ice-ages (a-c) and fluctuations of marine isotope stages (d) (redrawn after Gibbard & van Kolfschoten [33]). Refugia are marked by grey areas, expansions/retractions by arrows. 4a) Günz and Mindel refugia in Iberia (M. lachesis) and the Maghreb (M. galathea); expansion from the eastern Maghreb to Sicily during the Mindel/Holstein transition; Holstein expansion over Europe, but retraction in the Maghreb to the west. 4b) Riss refugia in Iberia (M. lachesis) and the western Maghreb, Sicily and southern Balkans (M. galathea; Riss/Eem transition expansion from Sicily to the eastern Maghreb; Eem expansion of the southern Balkan group over major parts of Europe including peninsular Italy. 4c) Würm refugia in Iberia (M. lachesis) as well as western and eastern Maghreb, Sicily, peninsular Italy, southwestern Alps and Balkan area (M. galathea); postglacial expansion from Iberia (M. lachesis), peninsular Italy and the Balkan area (M. galathea).

Atlantic-Mediterranean origin of the M. galathea/lachesis species complex: 

"The recent geographic restriction of M. lachesis to Iberia and the highest genetic diversity of M. galathea in Morocco support the idea of a centre of origin of the entire species complex in this area. This assumption is further supported by other Melanargia species mostly endemic to the Atlantic-Mediterranean region (M. occitanica, M. ines) and other endemics to further Mediterranean refugia (M. arge: peninsular Italy; M. pherusa: Sicily, M. larissa: Pontic-Mediterranean region and Iran). The onset of the differentiation between these sister species should be due to vicariance events most likely correlated with the onset of an ice age. If giving one glacial-interglacial cycle for the lowest level of differentiation (i.e. the subgroups within the two major M. galathea lineages), the most likely time horizon of this vicariance event is the onset of the Günz glaciation some 560,000 years BP [33] (Figure 4a). Since then, M. lachesis most likely has never expanded out of Iberia whereas M. galathea colonised most of Europe from its Maghreb expansion centre. Similar splits between Iberia and the Maghreb are commonly observed in many species groups [e.g. [13,34-36]]."

From the Maghreb to Europe:

"The deepest split in the M. galathea populations is between the Sicily - Tunisia group and all the other populations. As this split is about twice the genetic differentiation among their subgroups and less than half of the distance against M. lachesis, the onset of the Riss glaciation (about 310 ky BP) [33] might be the trigger for vicariance and thus the beginning of this differentiation. As (i) Iberia was continuously blocked for the expansion of M. galathea to Europe by M. lachesis [cf. 27] and (ii) all European M. galathea populations except Sicily are more similar to populations from Morocco than from Tunisia, a scenario with this split taking place in the Maghreb is little likely. This assumption is further supported by SDMs for ice age conditions predicting mostly continuous distributions over North Africa (Figure 3b) thus allowing vicariance in this region only during the relatively short interglacial stages. For these reasons, M. galathea must have reached Europe before the Riss glaciation."

"As the region of the eastern Sahara in Egypt apparently always have been too dry for an expansion of M. galathea, this first expansion of M. galathea to Europe must have been from Tunisia to Sicily (Figure 4a), a sea strait known for biogeographical connections for many taxa [e.g. [15]; and references therein]. As the Strait of Sicily was considerably narrower during glacial periods due to eustatic sea level lowering, the transition from Mindel glaciation to Holstein interglacial with still low sea level but already higher temperatures might have been a suitable time period for this dispersal. After arrival to Sicily, the Holstein interglacial might have given suitable condition for the expansion of M. galathea over most parts of Europe, including the Balkans but excluding Iberia as this peninsula was already populated by M. lachesis (Figure 4a)."

"With the climatic cooling of the Riss ice age [about 200 ky BP, see Timeline of Glaciation (link)], which was considerably longer than the following Würm glaciation and had longer durations of minimum temperatures[33,37], M. galathea most probably was nearly extinct in Europe only surviving in the southernmost possible retreats in Sicily and the southern Balkan (Peleponnesos), but also in the Maghreb; M. lachesis could survive in southern Iberia (Figure 4b)."

... and back to the Maghreb

"As the time for differentiation between the four M. galathea lineages from continental Europe is assumed to be the result of one glacial cycle (see above) and as the differentiation between populations from Sicily and Tunisia are in the same order of magnitude, we assume that the onset of this differentiation is in the same time frame. As the genetic diversity is significantly higher in Sicily than in Tunisia and the warm and dry interglacial climatic conditions in Tunisia generally unsuitable for the survival of M. galathea, we assume that a colonisation most likely has taken place from Sicily to Tunisia. While the sea level was still considerably lowered at the transition from Riss to Eem [about 130 ky BP, see Timeline of Glaciation (link)], thus facilitating dispersal between these two areas, this time period might be the most likely for this expansion event. During the following Eem interglacial [130ky - 110ky BP], the Balkan refuge of M. galathea most probably could colonise most parts of Europe apart from Iberia and Sicily, which were occupied by other genetic lineages of this species complex (Figure 4b)."

The existence of extra-Mediterranean refugia for thermophilic taxa

"During the Würm ice age [110ky - 12ky BP (link)], which was not more severe than the two previous glaciations but with a shorter maximum [33], the Marbled White butterflies were not that much pushed to the South than in the previous cases. This is well matching the remarkable differentiation of the species in Europe allowing to distinguish five lineages (see above), which most likely are the result of survival of the Würm ice age in a larger number of different refugia."

"This pattern implies at least two different refugia at the Balkan Peninsula at the western and the eastern flank; more in detail analyses also support a third Balkan centre in the peninsula's southern parts [29] (Figure 4c). This pattern of multiple refugia in the Balkans was already erected by Reinig [39] postulating different centres of survival in the western, southern and eastern Balkans and was later supported by genetic analyses showing genetic divergences between these areas for a variety of different animal species [e.g. [18,40-42]]."

"Furthermore, different Würm refugia have to be postulated for Sicily and peninsular Italy, a pattern also repeated by other genetic analyses [e.g. [17,43]]. Furthermore, other genetic studies show a remarkable genetic differentiation in the southernmost parts of peninsular Italy [e.g. [34,44,45]]."

"The last remaining lineage of M. galathea in the south-western Alps most likely is not representing a Mediterranean refuge of this species, but an extra-Mediterranean refuge area at the southern slopes of the glaciated Alps (Figure 4c). As already shown by Steward and Lister [46], glacial survival of temperate species in Europe was not only possible in the classical Mediterranean refugia sensu de Lattin [47], but also in small climatically buffered pockets in more northern regions [8,48,49]. Recent works especially highlight the southern and south-eastern parts of the Alps of particular importance for additional Würm ice age refugia for temperate species [e.g. [42,50,51]], and also for species formerly thought to be of exclusive Mediterranean origin [e.g. [52,53]]. This apparently was also the case for the Marbled White."

Postglacial expansion

"During the Postglacial [12ka BP to present (link)], several lineages of M. galathea were mostly blocked in their expansion by other lineages representing the respective leading edges [cf. 54]. In the case of M. galathea in Morocco, their northwards expansion was blocked by M. lachesis distributed in Iberia. The lineage surviving in the eastern Balkans apparently had the most important impact in the recolonisation of more northern parts of Europe as its dispersal was not hampered by any major mountain obstacle [cf. 9] so that this lineage could expand throughout Central Europe to the western parts of Germany (Figure 4c). However, the samples of north-eastern France and southern Germany show an intermediate genetic structure between this lineage and the south-western Alps lineage, making hybrid origin of these populations rather likely and thus expansion of the southern Alps lineage over the chains of the Alps."

"Also the Italian lineage could expand beyond its refugium to southern France. Therefore the entire region of northern France and southern Germany might be a zone of mixing between these three lineages. Hybrid zones between different taxa are frequently observed in this region [e.g. [9,55]]. Furthermore, the southernmost population in Calabria (southern Italy) has an intermediate genetic texture between the Italian and the Sicily group thus speaking for a postglacial contact and intermixing between these two groups in this region."

Sunday, November 4, 2012

For What They Were ... We Are on H1 in North Africa

Published in 2010 was the paper:

Mitochondrial DNA H1 in North Africa: 
An Early Holocene Arrival from Iberia
PLoS ONE 2010. (Open access (link))

Maju's very interesting comments on this paper are posted here: (link)

I would agree with Maju that the arrival of H1 in North Africa predates the Early Holocene.  I would also agree with comments on the association of H1 in North Africa with R-V88. 

What I would note is that the distribution of R-V88, with its association with Italy, Corsica, Sardinia and Africa, suggests a Strait of Sicily crossing rather than Iberia.

Regarding Maju's statement that the genesis of the Oranian culture is of an H1/R-V88 origin, I note that the transistion between the Aterian and Ounanian in North Africa is a current topic of interest regarding human origins.  A recommended reference is:

Modern Origins:  A North African Perspective
Editors:  Jean-Jacques Hublin, Shannon P. McPherron
(link)

Update:  The Oranian (wiki link) lithic culture to which Maju refers is not the same as the Ounanian lithic culture that is described in the Drake et al paper (link).  See comments in this post.  I believe the Oranian to which Maju refers is discussed as part of the late Aterian culture in the chapter "The Identity and Timing of the Aterian in Morocco" in the "Modern Origins: A North African Perspective", which is written by A. Bouzouggar and R. N. E. Barton.  That is not to say that the Aterian, Ounanian and Oranian are not related.

Saturday, November 3, 2012

Population expansion in North African Late Pleistocene signalled by mitochondrial DNA haplogroup U6


Figure 1.  Interpolation Map representing the centroids of sampling locations used for the spatial smoothing analyses of haplogroup frequencies (based on HV-I data sets). The resulting frequency maps are shown for U6 (B), U6a (C) and U6bd (D).

Pereira et al
BMC Evolutionary Biology
(link)

Conclusions: A Bayesian skyline plot placed the main expansion in the time frame of the Late Pleistocene, around 20 ka, and spatial smoothing techniques suggested that the most probable geographic region for this demographic event was to the west of North Africa. A comparison with U6’s European sister clade, U5, revealed a stronger population expansion at around this time in Europe. Also in contrast with U5, a weak signal of a recent population expansion in the last 5,000 years was observed in North Africa, pointing to a moderate impact of the late Neolithic on the local population size of the southern Mediterranean coast.

Update (November 3rd, 2012): The above paper was discussed on the "For what they were ... we are" blog in December of 2010 (link). Maju brings up some very interesting points which I would like to elaborate upon [my comments added in blue]:

Maju: An interesting paragraph, which I'd like to discuss is the following one (from the conclusions section):

The recently revised archaeological dates for the Aterian industry of North Africa emphasize that the makers of this industry do not appear to have left any imprint in the maternal lineages of present-day North Africans. The oldest arrivals amongst extant mtDNAs appear to be the U6 and M1 lineages, which date to 36.6 (24.9; 48.8) and 25.4 (17.9; 33.1) ka respectively [31]. As with U5 in Europe [11], the arrival time could be older in each case, since the haplogroups appear likely to have arisen within the southern Mediterranean region from haplogroup U and M ancestors, making dating the arrival time very imprecise. Nevertheless, the estimates seem to match best the appearance of the Upper Palaeolithic Dabban industry in Cyrenaïca, as suggested before [15,23].

Maju: I do agree that the antecessor of U6 (and maybe also M1) arrived in North Africa most likely with the Dabban industry and that the chronology estimates confirm that (roughly). However I disagree when they claim that Aterian industry left no genetic legacy. This claim is unfounded because they ignore the L(xM,N) lineages which make up some 25% of North African mtDNA and at least in many cases must be from a time frame older than the Dabban industry, as I discussed in my old blog.

[Marnie: The other possibility is that early U was a trans continental haplogroup in both North Africa and Europe that later expanded in the northwest of Africa and northward into Europe. In that case, U6 would be African and descended from U in Africa. U5 would represent an early Out of Africa expansion across the Strait of Gibraltar or the Strait of Sicily.]

Maju: Another substantial disagreement I have is when they claim that:
Aside from U6, North Africa was also the recipient of European, Near Eastern and sub-Saharan African lineages most of which most likely arrived in the Holocene. Haplogroups H1, H3 and V expanded in Iberia in the Lateglacial/postglacial [11,58-61], and evidently spread into North Africa from Iberia across the Gibraltar Straits, most likely in the early Holocene [62-65].

Maju: This comes from a calibration error, arbitrarily deciding that H1, H3, V and others (H4, H7) as having expanded only after the Last Glacial Maximum. In turn this stems from a fundamental misunderstanding of what archaeologically makes sense: that the only moment of clear contact between SW Europe and North Africa is at the genesis of Oranian culture, which shows clear influence from the peculiar Iberian Gravetto-Solutrean complex (and in turn Iberian Gravetto-Solutrean later shows influence from North African fashions, notably the back-tipped arrow or spear points). While there is lesser connection between Iberia and some scattered coastal spots of North Africa in the early Holocene (Neolithic) with the Cardium Pottery culture this cannot justify almost 30% of the North African mtDNA. There is a more important later "Iberian" influence in North Africa with the Megalithism, however it is hard to explain why these very late hypothetical colonists contributed so much in the maternal genetic pool and so little in the paternal one, not to mention that non-Megalithic Guanches (Canary Island natives) also show more (fossil) Y-DNA R1b and I (17%) than modern mainland North Africans (discussed here).

Maju: The reality of this situation will be better understood when DNA chronologists accept that the timeline of mtDNA H (and V) is older than usually accepted and comparable to that of U, if not even older. In any case my calibration point for these lineages (H1, H3, H4, H7 and V) is precisely the unique trans-Mediterranean connection episode that happened almost without doubt at the genesis of Oranian culture. It is the only safe calibration point, what means that these lineages were formed and consolidated in SW Europe prior to that expansion into North Africa, so they must be at least of Gravettian time-frame (which is c. 22 Ka for Mediterranean Iberia), because Solutrean proper had a very limited presence in this area (two nearby caves in Valencia), even if it gradually modified the strong Gravettian substrate (and was modified by it).

[Marnie:  I agree that there is no clear basis for the expansion of H only during the Holocene.  The likelihood is that it is an expansion associated with the lower sea level in the Mediterranean during the LGM and up until the early Holocene.  In addition to the Strait of Gibraltar, the crossing point could be the Strait of Sicily. The distribution of H1 in North Africa, concentrated on the east side of the Atlas Mountains, favors the Strait of Sicily crossing.  A crossing at the time of the LGM would have favored the Strait of Sicily, as the southern Iberian peninsula was likely climatically less favorable than Tunisia and Sicily at this time.]