Saturday, June 30, 2012

Parallel Domestication of Food Crops

 
Qasr Ibrim, as photographed by the Allaby Research Group (Link)

This recent paper from the Allaby Research Group discusses the case for parallel domestication of food crops in diverse regions of the world.  Its focus is on agricultural crops, so it is not directly related to the process of cattle domestication.  However, the discussion in the paper of an independent domestication of cotton at Qasr Ibrim supports the notion of a localized agripastoral tradition on the Nile.  Related to this discussion is the previous post which mentions cotton domestication among Saharo-Sahelian speakers.

The blossoming of plant archaeogenetics
Sarah A. Palmer, Oliver Smith, Robin G. Allaby
Annals of Anatomy, Volume 194, Issue 1, 20 January 2012, Pages 146-156
(Link)

Introduction:

"For the past two decades scientific drivers concerned with the origin and spread of domesticated crops have dominated the utility of ancient DNA from plants (Fig. 1). It is a current aspiration that genomic studies of plant remains could unlock critical evidence of the origins of domestication and strengthen the bridge between phylogenetic studies of modern plants and the archaeology of plant remains (archaeobotany). This study of plant domestication has itself undergone substantial change in recent years in response to new data leading to a different framework of understanding. The interpretation of phylogenetic data with regard to domestication is often seated on the framework of models of human behaviour in the shift from hunter-gathers to agriculturalists ( [Allaby et al., 2008] and [Allaby et al., 2010]). However, theses based on plant phylogeny, which uses extant allelic diversity to infer past genomic events, and archaeobotany, which examines archaeological plant remains by morphology, have sometimes appeared to contradict one another. Recently, mounting archaeological evidence has spurred a shift in thinking from a rapid transition paradigm for the shift from hunter-gatherers to agriculturalists in which a ‘Neolithic package’ of staple food crops were domesticated over a relatively short time period by a small farming group, to a protracted transition paradigm in which domestication of food crops occurred in parallel, over a long time, in diverse regions worldwide (Fuller et al., 2010). The interpretation of genetic diversity needs to be reviewed in light of the modified genetic expectation of the paradigm of protracted transition (Allaby, 2010)."

Reconstruction of the early history and movement of cultivated plant species:

"The arguments for the origin of crop species and movement of these species to where they can be found today are largely dependent on genetic diversity. With the classical underlying expectation of a rapid transition paradigm (where domestication events are discrete and quick), monophyly or polyphyly has been interpreted as evidence of single or multiple origins, respectively (Allaby et al., 2010). Archaeogenetics has been used in parallel with these studies to mine for past allelic diversity (Navascues et al., 2010). Phylogenetic analysis to determine centre of origin and movement has been undertaken of archaeobotanical remains of many of the crop species important to human societies, including members of the cucurbitaceae ( [Szabo et al., 2008], [Zoltan et al., 2007] and [Erickson et al., 2005]), the poaceae ( [Nasab et al., 2010], [Li et al., 2011], [Tanaka et al., 2010], [Lia et al., 2007], [Gyulai et al., 2006], [Lagler et al., 2005], [Lagler et al., 2006], [Freitas et al., 2003] and [Allaby et al., 1999]), grapes ( [Cappellini et al., 2010] and [Manen et al., 2003]), the Prunus genus (Pollmann et al., 2005) and olives (Elbaum et al., 2006)."

"The most extensively archaeogenetically characterised gene family is that of the high molecular weight glutenin gene (Glu) in wheats. The Glu genes have a conveniently short polymorphic region in the promoter that is ideally suited for the identification of alleles unique to hexaploid bread wheat ( [Allaby et al., 1999] and [Nasab et al., 2010]). Recently, Li et al. (2011) discovered the Glu D genome allele in Bronze Age wheat samples from China indicating hexaploid bread wheat. This is in contrast with archaeobotanical evidence of tetraploid emmer wheat predominating Western Eurasia. This finding echoes previous studies in which the D genome was similarly identified in an assemblage from Bronze Age Greece that was thought to be tetraploid wheat only (Allaby et al., 1999). Furthermore, an entirely extinct expansion of wheats into Europe containing the more unusual G genome was initially detected through ancient DNA (Brown et al., 1998), a finding that was later confirmed by archaeobotany (Jones et al., 2000). A similar pattern of replacement has been observed in recent studies of early Japanese rice agriculture which suggest that tropical rice varieties were grown which were later replaced by temperate varieties (Tanaka et al., 2010)."

"Ancient DNA as a marker of phylogeographic stability has also been used with maize ( [Freitas et al., 2003] and [Lia et al., 2007]). In this case the primitive landraces used by Native Americans in South America were used to establish a modern phylogeographic distribution of alleles of alcohol dehydrogenase and microsatellites the antiquity of which was confirmed with archaeobotanical samples, giving a picture of a distinct east west divide suggestive of two expansions of maize into South America from the meso-American homeland of maize. The establishment of 10,000 year old remains in the New World as bottle gourd (Lagenaria siceraria) sets an important biogeographic precedent in that it establishes that paleoindian populations transferred domesticated plants from the Old World, despite their hunter-gatherer life-style (Erickson et al., 2005). Until then evidence that they had been associated with any plant transportation had been scant."

"More recently, archaeoegenetic studies which have exploited herbarium samples of barley to expand the sample set to include extinct landraces and cultivars sampled where they are no longer grown today, facilitated resolution of genetic structuring on a fine geographical scale in Sweden that would have been unavailable from modern crops (Leino and Hagenblad, 2010). In a similar case to that of the maize, in this latter study the distribution is suggestive of two entries of barley into Sweden suggestive of two cultural influences."

Paleoethnobotany:

"Archaeological plant remains are also studied for the integral part they play in human society. Often excavated in close proximity to remains of humans or their dwellings, plant remains can be examined in light of what plants were being produced, foraged, eaten, traded, or used in some other way. The marriage of archaeogenetics and ethnobotany is one of the most interdisciplinary of the sciences, and is characterised by the interpretation of archaeobotanical phylogenetics in light of theories formulated from archaeology. Archaeobotanical reconstructions are frequently hindered by ambiguous identification of samples (Schlumbaum et al., 2008). Archaeogenetics has been used as a tool for species identification where the morphology is ambiguous."

"A common use of archaeogenetics on ethnological remains has been to reconstruct diets of past peoples including the vegetal dietary elements ( [Rasmussen et al., 2009], [Rollo et al., 2002] and [Poinar et al., 2001]). Of archaeobotanical remains, the inferences of resolved identification have been used to confirm an indigenous independent domestication of the A genome cotton, Gossypium herbaceum in Africa prior to Asian influence (Palmer et al., unpublished) and several instances of hexaploid bread wheat during the Bronze age in China (Li et al., 2011) and Greece (Allaby et al., 1999), much earlier than previously estimated in the former case. Also, the use of Prunus spinosa and P. avium/cerasus by the Romans in the Northern alpine region has been established (Pollmann et al., 2005)."

"The mode in which archaeological remains were used and the evaluation of the importance of trade versus local agricultural diversity have also been areas of ethnobotany where archaeogenetics has made valuable contributions. In our lab, we have examined Barley and Cotton remains from Qasr Ibrim, a border settlement on the River Nile that was subject to numerous cultural transitions. Samples of barley from all six strata examined, spanning more than 3000 years, displayed the same allele at the vrs1 locus (Palmer et al., 2009). Given the settlement's situation on the trade route of the River Nile, it was considered likely that conquering peoples may have introduced foreign germplasm to the area. However, this local landrace appears to have persisted throughout the occupation of this settlement. The identification of the cotton remains at this site as G. herbaceum, suggests local production, rather than the opposing theory that cotton was generally imported from Asia and processed locally."

The Saharo-Sahelian Peoples and the Beginnings of Crop Cultivation

Excerpted from The Civilations of Africa:  A History to 1800, "Chapter 3:  Culture and Technology in Africa, 8500-3500 BCE" by Christopher Ehret, 2002.

The Saharo-Sahelian Peoples and the Beginnings of Crop Cultivation

"Sometime between 8000 and 7000 BCE, the Saharo-Sahelian descendants of the Northern Sudanian people set in motion an economic shift of even greater social and cultural impact:  they began the first deliberate cultivation of at least  some of the grains - sorghum may have been one - that they previously had gathered as wild.  The timing of this development may have something to do with the still further increase in rainfall at this particular period.  More rainfall meant more areas of the Sahara in which sorghum could be successfully grown and so would have made grain cultivation seem a less chancy venture than it would have been before. (Our knowledge of the next several thousand years of pre-Kunama history is virtually nil, so the remaining discussion focuses on the Saharo-Sahelians, who in any case seem to have been the major innovating group of peoples.)

"The keeping of cattle had previously added considerably to the meat resources of the Northern Sudanic lands, otherwise poorly endowed with large mammals.  But with cultivation the Saharo-Sahelians created a set of subsistence practices that gave them the potential, over the long run of history, to expand their food supply many times over and to support a growing population.  We can call the set of crops and the cultivating practices pioneered by the Saharo-Sahelians "Sudanic seed agriculture" or just "Sudanic agriculture."  The term "seed" is included to bring attention to the fact that the key crops of this agriculture were all propagated from seed.  We sometimes also call the combined livestock-raising and cultivating practices of these peoples the Sudanic "agripastoral" tradition.  Progressively over the period between 7000 and 5000 BCE, the Saharo-Sahelians and their descendants brought under cultivation new crops in addition to sorghum, domesticating more of the indigenous wild food plants of the region - first, before 6000 BCE, a variety of gourds and calabashes including the edible gourd, and then, by perhaps 5000 BCE, cotton, pearl millet, and watermelons."


Related Posts:

The onset of food production among Proto-Northern Sudanic speakers (Link)
Origins of Nilo-Saharan and Cushitic Speakers (Link)

Friday, June 22, 2012

A Date for Dairying in the Green Sahara

Thank you once again to the forwhattheywereweare blog for the post Dairying in Africa some 7000 years ago (link).  This post discusses a Nature paper which establishes a date for dairying at Tadrart Acacus on the border of Tassili N'Ajjer in Algeria.  Several press announcements also cover the paper:

Chemical analysis of pottery reveals first dairying in Saharan Africa in the fifth millenium BC
University of Bristol Press Release
(Link)

Data:  7,000 years ago, Saharan Africans milked cows, made cheese
LA Times Science Article by Thomas H. Maugh II
(Link)


Related Post:

Tishkoff on the origins of pastoralism in Africa (Link)

Tuesday, June 19, 2012

Kuri Cattle of Lake Chad

Nomads of the Islands [of Lake Chad]

The Kuri cattle of Lake Chad are an unusual and sadly rapidly disappearing breed of cattle. They are adapted to the Lake Chad region.  It is unclear at this point as to whether they were domesticated in Lake Chad, the Nile, or somewhere else.  Traditionally, they have been known for their highly unusual horn shape, as discussed here in this database.  With the disappearance of Lake Chad, the survival of lake adapted Kuri cattle is under threat as herders struggle to hybridize their animals with more drought tolerant breeds.  In this video, their are no animals with the traditional bulbous Kuri cattle horns, showing that the nomads in the video have already hybridized their herds.  Although the bulbous horns are not preserved in these herds, these cattle clearly have preserved their lake adapted Kuri cattle swimming ability.

Related Post:

Lake Chad (Link)

Monday, June 18, 2012

Recent Comments added to sidebar

I've added a "Recent Comments" list to the sidebar on the right to assist readers with tracking recent comments.  Also, I know the blog is taking a little longer than usual to load.  There is a lot of visual content on the current posts.  Thanks for your patience.

Saturday, June 16, 2012

Friday, June 15, 2012

Reconsidering the Spread of mtDNA T1 Cattle

Origin and Spread of Bos taurus:
New Clues from Mitochondrial Genomes Belonging to Haplogroup T1

Bonfiglio et al
(Link)

I've been looking at this paper over the last week, since I first came across it at the forwhattherewereweare blog.  The sequencing in this paper is impressive in the number of samples analyzed and the granularity of the sequencing conducted.  The authors posit that the distribution of type T1 mtDNA cattle shows a spread from the Near East with domestication.

Without commenting immediately on this conclusion, I will mention that the authors construct from their T1 data an evolutionary tree shown in Figure 1, below.  This tree is complete with geographic position of breed and time estimates obtained using maximum likelihood statistics (Table 3).

There is a slight unexplained mismatch between the time estimates labelled on Figure 1 and those in Table 3, which unfortunately places the time estimates into question.  Additionally, there are some researchers (See "Pylogenetic analysis", Lari et al (Link)) that question the current classification system for bovid sub-clades.   Therefore, the data shown in Figure 1 need to be examined with these limitations in mind. 

However, the overall distribution of the T1 clades is very interesting with respect to the history of both African and Italian cattle.

Figure 1.  Tree of Complete Bovine mtDNA Sequences Belonging to Haplogroup T1.

Looking at the distribution for T1 cattle shown in Figure 1, it might be tempting to conclude, due to the many European samples of T1, that T1 carrying cattle must have reached Europe from the Near East by way of a northern route.  However, a closer examination of the locations of the European samples reveals an alternate possibility.  (See below, List of T1 European Cattle).  Most of the European samples in the T1a and T1b haplogroups are for Italian cattle.  The small number of European samples in the T1c haplogroup are either Italian or Portuguese, with one outlier for a Friesian cattle sample. This distribution for T1 cattle opens the possibility that the Italian T1 cattle arrived in Italy by crossing the Strait of Sicily at an early date from North Africa.  Also possible is an Italian origin for T haplogroup cattle.

At first, it might seem very implausible that this could be the case.  However, it is known that the Mediterranean sea level was more than 100 meters lower than today during the Last Glacial Maximum (Link).  Even 10 kya (kilo years ago), the crossing was less than 40km wide.  A recent dating of auroch drawings in Qurta, Egypt show that cattle were present there prior to 15,000 kya. Rock art experts note the similarity in style of the Qurta drawings to the rock art in Southern Italy, Sicily and Cyrenaica near the coast of northern Libya (Link).

If there was a crossing of mtDNA T cattle at the Strait of Sicily, the earliest crossings may have occured at a date prior to 11,450 kya, for there are samples of T type mtDNA auroch remains at Vado all'Arancio in Italy dated to this time. (Link)

It should be pointed out that with the exception of the above mentioned Italian and Portuguese cattle, the distribution of the T1b, T1c, and T1d cattle samples shown in Figure 1 point to a Northeast Africa origin for T1 type mtDNA cattle.

The branching of T1 cattle from that of other T cattle is dated, by maximum likelihood statistics, to approximately 12.5 plus or minus 2.3 kya.  That's a wide window, which makes it difficult to determine exactly when the ancestors of mtDNA T1 cattle might have arrived in northwest Africa.  (The branching of mtDNA T from the QT branch is dated to approximately 48kya (Link), with very few of the Q lineages of cattle showing up in Africa.)

More research is needed to verify and time the branchings of the T1 mtDNA sub-clade from T1'2'3, T and QT mtDNA cattle lineages.

However, the possibility that T1 carrying cattle crossed the Strait of Sicily prior to a significant sea level rise is plausible, as is genetic evidence for the survival of mtDNA T cattle lineages who's ancestors lived in North Africa more than 11,000 years ago.

Update (June 16th, 2012):

Morpho-Structure and Paleogeogeography of the Sicily Channel (Link) maps the Strait of Sicily.  The paper contains a map that can be  clicked into and then "zoomed".

List of T1 European Cattle
Figure 1, mtDNA T1a cattle: 
Origin of European Cattle in this group are:
1 - Agerolese - Agerola, southern Italy
2 - Chianina – Chiana Valley – central Italy – draught animal
3 - Maremmana - west central Italy
4 - Italian Podolian - Italy
5 - Marchigiana - cross of Podolian, Romagnola, Chianina – Italy
6 - Italian Brown - Italy
7 - Chianina – Chiana Valley – central Italy – draught animal
8 - Romagnola  - Italy
10 - Angus mix
11 - Chihuahua Creole - Mexico
13 - Marchigiana - cross of Podolian, Romagnola, Chianina – Italy
14 - Cinisara – Cinisi, Sicily
15 - Cinisara – Cinisi, Sicily
16 - Agerolese - Agerola, southern Italy
17 - Chianina – Chiana Valley – central Italy – draught animal
18 - Limousin - Southern France
19 - Maremmana - west central Italy
20 - Chianina – Chiana Valley – central Italy – draught animal
21 - Chianina – Chiana Valley – central Italy – draught animal
22 - Italian Podolian - Italy
23 - Romagnola - Italy
24 - Maremmana - west central Italy
25 - Chianina – Chiana Valley – central Italy – draught animal
28 - Marchigiana - cross of Podolian, Romagnola, Chianina – Italy


Figure 1, mtDNA T1b cattle
Origin of European cattle in this group are:
29 – Cinisara – Cinisi, Sicily
30 – Marchigiana - cross of Podolian, Romagnola, Chianina – Italy
31 – Cinisara - Cinisi, Sicily 
35 – Chianina – Chiana Valley – central Italy – draught animal
36 – Marchigiana - cross of Podolian Romagnola, Chianina - Italy

Figure 1, mtDNA T1c cattle
Origin of European cattle in this group are: 
44 – Cinisara - Cinisi, Sicily
46 – Friesian - Dutch
47 – Alentejana - Portugal
48 – Alentejana - Portugal
51 – Romagnola - Italy

Sunday, June 10, 2012

The Aurochs of Qurta

Maju at the forwhattheywereweare blog, alerts me to the recent dating of Egyptian rock art drawings of aurochs at Qurta on the Upper Nile.

These dated drawings indicate that aurochs (bos primigenius) were present south of the First Cataract, earlier than 15,000 years ago.

Egypt:  The Aurochs of Qurta (Link)
The Aurochs of Qurta:  Egyptian 'Ice Age' Art (Link)

Friday, June 8, 2012

Kerma et les débuts du Néolithique Africain

Matthieu Honegger
Mission Archéologique Suisse au Soudan
(Link)

translated from French
pages 246-247

"The difference between the tombs attributed to the Mesolithic and the cemeteries of the Neolithic are fundamental.  On one side are the small number of burials, without grave goods, all of equal status; on the other is a veritable necropolis with at least one hundred graves often with grave goods indicative of the emergence of social distinction.  In a millenium, Nubian society had completely transformed their social organization.  This transformation must have taken place on account of the introduction of domestic cattle, the oldest findings of which are in the Middle Nile at Nabta Playa in Egypt and Kerma (Fig. 1 [map]).

"Until the Winter of 2004-2005, the status of the Neolithic cemetery of El Barga was assumed, because of the presence of polished stone objects (axes, pendants, earrings, labrets), to be associated with the Mesolithic (Fig. 14 and 15).  The last discovery of the 2004-2005 campaign confirmed our hypothesis that El Barga is a Neolithic site:  a man's grave next to which was deposited the skull of a domestic cattle buried just above the burial of a child (Fig. 17).  Two carbon 14 dates have given results of approximately 5750 BC [7762 bp] that make this the oldest Neolithic site in the Nile Valley.  However, these dates don't correspond to the first phase of the Neolithic in the region.  In effect, the cemetery shows technical and social transformations that had already taken place and one can't doubt that the introduction of pastoralism had occured at an earlier time.

"The discovery of two sites located five kilometers from El Barga confirmed this hunch.  These two well-preserved habitats present a large quantity of objects on the surface, as well as the remnants of circular stone structures marking the location of huts.  A recovery of objects and animal remains from the surface and a survey has been conducted at the two sites to understand the stratigraphic sequence of the area.  The sites have a homogeneous occupation history across time, and contain the bones of domestic cattle.  Some of the remains were dated by radiocarbon dating to approximately 7000 BC [ 9000 bp]."

Thursday, June 7, 2012

Continuing Legacy: Preserving and Adapting Indigenous African Livestock


International Livestock Research Institute (Link)

There is more livestock diversity in Africa than on any other continent. Some indigenous breeds of cattle, [including the N'dama breed], goats and sheep are disease resistant, and others can withstand feed and water shortages. But most are less productive than some imported breeds and so do not meet farmers needs.

Millions of poor livestock keepers are importing animals, or cross breeding with imported breeds to get more productive livestock. But imported breeds need expensive care because they are much less hardy,
and animal deaths are increasing.

There is a danger that many of Africa's indigenous hardy livestock breeds will disappear, just as climate changes and population growth is making their hardy traits increasingly important for food security across the region.

This film tells the story of a unique research and development project that aims to increase understanding of trypanotolerant livestock and the people who rear them along with what is needed to improve markets and processing for livestock products. This information will then be combined with better feeding and breeding schemes, farmer training and policy changes to make indigenous animals more profitable for poor farmers, so that their future use becomes sustainable.

Reference:

International Trypanotolerance Centre (Link)

Monday, June 4, 2012

Domesticating Animals in Africa: Implications of Genetic and Archaeological Findings

Diane Gifford-Gonzalez and Olivier Hanotte
(Link)

Abstract:

"Domestication is an ongoing co-evolutionary process rather than an event or invention. Recent zooarchaeological and animal genetics research has prompted a thorough revision of our perspectives on the history of domestic animals in Africa. Genetic analyses of domestic animal species have revealed that domestic donkeys are descended from African ancestors, opened a debate over the contribution of indigenous aurochs to African domestic cattle, revealed an earlier and possibly exogenous origin of the domestic cat, and reframed our vision of African dogs. Genetic diversity studies and mapping of unique traits in African cattle, sheep, goats, pigs and chickens indicate adaptations to regional environmental challenges and suggest hitherto unknown and complex patterns of interactions both among Africans and with Southwest Asia and other Asian regions on the Indian Ocean. This article argues against the static perspective on domestication as invention and for viewing it as a dynamic, locally based and continuing process."

Cattle:

"Honegger ( 2005, "Kerma et les débuts du Néolithique africain", Genava n.s., 53, 239–249) reports two ‘Neolithic’ sites, south of the Nile’s Second Cataract and east of the locale of the later Kerma civilization, that have yielded remains of domestic cattle with an associated date of c. 7000 BC. Geographic proximity of these Nubian occurrences to the Nabta–Kiseiba region suggests domestic cattle appeared first in the grassy hinterlands of the Nile in this region, as dates for cattle remains are oldest in the eastern Sahara–Sahel and youngest in the far western Sahara."

Sunday, June 3, 2012

Chris Ehret Book: The Civilizations of Africa

Over the last several weeks, I've been reading The Civilizations of Africa:  A History to 1800 by Christopher Ehret.  This book was published in 2002 and is based upon Ehret's work as a linguist studying African languages.  The Amazon link for this book can be found here.

The book describes the placement and economy of early Afroasiatic, Nilo-Saharan, Niger-Congo, Khoisan and BaTwa communities starting at approximately 21,000 ybp.  He describes how each of these communities employed and developed food acquisition methods in response to changes in their local climates.

Relevant to the discussion of domestication on the Nile is Ehret's description of two distinct cultures:  The proto-Afroasiatic culture originating along the Red Sea Hills and northern Ethiopian highlands and the proto-Nilo-Saharan culture of the middle Nile.  Map 4 of the book illustrates the proposed locations for these proto cultures:
It is proposed that the proto-Afroasiatic (Afrasan on the map) culture was initially focused on the collection of grains from wild grasses.  The proto-Nilo-Saharan speakers where intially hunters of large game as well as fishermen who gradually split into two groups, with one specializing in an agripastoral economy and the other focusing on aquatic resources along rivers.  During the initial development of these cultures, Afroasiatic and Nilo-Saharan speakers were separated by 300 to 400 kilometers of uninhabitable Sahara desert and by the cataracts of the Nile.  In recent posts on Nile domestication, an archaeological site representative of the early Afroasiatic tradition would be Wadi Kubbaniya (post).  Early Nilo-Saharan peoples are believed to have lived at the confluence of the White and Blue Nile (post).

These groups gradually expanded outwards from their homelands, especially after 10500 bp during the phase of the green Sahara.  Ehret refers to this phase as the Holocene Climatic Optimum.  (On this blog, it has previously been referred to as the Great Wet Phase of the Sahara.)  Ehret points out that during these expansions, the Afroasiatic and Nilo-Saharan cultures came into contact with each other.  There is linguistic evidence of cultural exchange, including the exchange of knowledge about plant and livestock cultivation.  The forms of exchange are quite detailed and I would be doing the author a disservice to copy his recently published work directly on this blog.

Ehret's book is available on Amazon for a modest price. I have read the first four chapters and  I believe the book deserves at least four stars, so don't be fooled by the review of one disgruntled reader.  In addition to the in depth discussion on Afroasiatic and Nilo-Saharan cultures, there is the remarkable early history of Niger-Congo, Khoisan and BaTwa peoples.  African domestication of various crops such as cotton, sorghum, yams, millet, black-eyed peas, palm oil and African groundnut are explored. The book is easy to read and does not require any specialist knowledge of African archaeology or linguistics.

Regarding the recent discussion on this blog, Ehret's linguistic deductions do support the assertion that cattle were domesticated independently by the Nilo-Saharans at about 10,000 bp.  He also suggests that Afroasiatic speakers of the Red Sea hills may have engaged in a form of "protection of wild cows".  As of the 2002 publication, Ehret stated that the exchange of knowledge regarding cattle herding between Nilo-Saharans and Afroasiatic speakers of the Red Sea hills is as yet poorly understood.