Posts Tagged ‘AMH’

Ancient Chinese teeth confirm many and older Out of Africa events

October 15, 2015

Over at 6,000 generations I post about the new paper about the 47 human teeth found in Fuyan Cave, Daoxian, China which are between 80,000 and 120,000 years old.

The 47 human teeth found in Fuyan Cave, Daoxian, China. photo S. XING AND X-J. WU via DiscoveryNews

There were clearly many Out of Africa or Africarabia events starting from 130,000 years ago both before and after the Toba explosion.

80,000-120,000 year old modern humans in S China confirm many and older Out of Africa events

The single Out of Africa event for modern humans is clearly far too simplistic. It is also clear that there were many back to Africa movements as well. Humans expanded sometimes because their old habitats were no longer viable. But, it seems, humans also explored and expanded into new territories from regions of plenty and where they maintained some contact with where they had come from. Probably, just because they could.

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Promiscuity in the pleistocene

January 2, 2014

Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology and his colleagues from various institutions are making stunning advances in the analysis of ancient DNA. The complete genome of a Neanderthal has now been reconstructed with a remarkable level of detail.

The complete genome sequence of a Neanderthal from the Altai MountainsKay Prüfer et al, Nature 505, 43–49 (02 January 2014),  doi:10.1038/nature12886

Editors Summary: Recent excavations in the Denisova Cave in the Altai Mountains of southern Siberia have yielded a wealth of hominin fossils from a site that has been occupied for perhaps 250,000 years or more. Now a high-quality genome sequence has been determined from a circa 50,000-year-old toe bone — a proximal toe phalanx — excavated from the east gallery of Denisova Cave in 2010. The sequence is that of a Neanderthal woman whose parents were closely related — perhaps half-siblings or uncle and niece. Such inbreeding was also common among her recent ancestors. Comparisons with other archaic and present-day human genomes reveal several gene-flow events among Neanderthals, the closely related Denisovans and early modern humans, possibly including gene flow into Denisovans from an unknown archaic group. The high-quality Neanderthal genome also helps to establish a definitive list of substitutions that became fixed in modern humans after their separation from the ancestors of Neanderthals and Denisovans.

promiscuity in the pleistocene

But what is also becoming clear is that there were more “species” of homo erectus who existed in parallel than has generally been assumed and also that sexual encounters and interbreeding between these cousin-species has been a regular occurrence over some 250,000 years. And so there have been times when Anatomically Modern Humans (AMH), Neanderthals, Denisovans and the “unknown” hominim have co-existed.

The AMH-Neanderthals split is thought to have occurred about 400,000 years ago. The split with the unknown hominims then must have been around 500,000 years ago. The Denisovans split off from the Neanderthals perhaps about 300,000 years ago. The Out-of-Africa split among AMH was around 100,000 years ago.

A Neanderthal in our time. (copyright Nenderthal Museum / H Neumann)

A Neanderthal in our time. (copyright Nenderthal Museum / H Neumann)

These ancient splits were all probably in and around Africa even if the Out-of-Africa event for AMH is now more likely to have been  many such events and an expansion out of Africarabia. But it also means that a wave of “unknown hominims” split off from the mainline after a mainline group had left Africa and then spread out to unknown areas. Neanderthals probably split from their parent line of descent also outside of Africa but there must first have come a migration from Africa. The Neanderthal-Denisovan split must also have taken place outside of Africa. Clearly there have been many migrations Out of Africa over the last 400,000 years.

Carl Zimmer writes, “Evolution is a mixture of flow–the cascade of genes from parents to offspring, and the criss-cross movement between populations and species”.

But this generates a myriad of new questions. How large were the troops or tribes or clans of these ancient hunter-gatherers that they could sustain such large migrations? For how long and in what proximity did these different species of man co-exist. These troops – it is thought – probably did not number more than about 50. Some critical population would have been required for sufficient interactions to have taken place between the species. At any one time the total human population – of all species – may have approached 10 million (for if this was – say – just 1 million the opportunities to interbreed would not have been many). They all had fire, but did they all have some form of speech?

But most fascinating of all is how the interbreeding took place. Was it just a product of normal rape and pillage? Did violent clashes lead to the victors impregnating the vanquished, or were there other scenarios for individuals to mate? At some point there must have been children who were 50% Neanderthal and 50% AMH. And some who were 50% Neanderthal and 50% Denisovan. How did they survive? What kind of society existed in these ancient times that would permit such offspring not only to survive but also to mate and produce offspring in their turn? But however it happened, our ancestors in the pleistocene were a promiscuous lot.

Could it be that it was only among AMH  – after they had been vanquished and raped and pillaged by Neanderthal raids – that such mixed children were allowed not only to survive but also to thrive?

The next 100,000 years

June 1, 2013

In my other blog I try to address the life and times of the last 6,000 generations but trying to look forward to the next 6,000 is a fascinating thought experiment.

I was looking at the history of glacials and interglacials and just thinking that it was was terribly “unfair” that while I could imagine the future to my mind’s content, I could never know it. At least for even the distant past, we can look at surviving clues and by the logic that the past must have led to the present we can fill in the gaps and imagine what must have happened. The present constrains the past and helps to keep the imagination within narrow bounds. But for the future, the present  provides a starting point  and natural laws must also constrain any development of an unfolding future. But there are more natural laws we don’t know about than we do. And we haven’t a clue about all that we don’t know that we don’t know.

But I am still free to imagine what the next 100,000 years may bring.

As best we can judge, interglacials (defined as being when temperatures are higher than or equal to those at present)  have lasted upto 28,000 years and some seem to have been as short as 4,000 years. However most seem to last around 13,000 years. This interglacial period will surely end – whether within a 1000 years or in 10,000 – and a new glacial period will ensue.

http://roperld.com/science/sealevelvstemperature.htm

interglacials

But the next glacial will be different for humans and primarily because we have access to “abundant energy” (mainly based on fossil fuels and nuclear energy).

(more…)

Migration from India brought genes, tools and dingoes to Australia 4,200 years ago

January 15, 2013

It is generally assumed that the expansion of AMH from Africa (or Africarabia) reached S-E Asia around 70,000 years ago and Australia some 40,000 – 50,000 years ago. The Australian population then remained virtually isolated until quite recently. But a new genome-wide study suggests that there was migration from India to Australia some 4,200 years ago during the Holocene and that they brought stone-tools and the ancestor of the dingo with them. The study suggests that after the first migrants originally arrived in Sahul, the Australian, New Guinea and Mamanwa populations split from each other some 36,000 years ago. But by – an as yet unknown route – migrants from India arrived in Australia between 4,000 and 5,000 years ago.

Though this coincides with the height of the Indus Valley civilization in 2600 BC, I think it is more likely that any ocean-based, island-hopping migration at this time would have started – at least geographically – from S-E India rather than from the Indus Valley civilization in N-W India. But coastal navigation around the Indian coastline of that time would have been well within the capabilities of the Indus valley inhabitants. This is also the period when proto-Dravidian was the language across most of India (including in the Indus valley civilization) and it would be interesting if there are any traces in language which match this genetic data.

Genome-wide data substantiate Holocene gene flow from India to Australia, by Irina Pugach, Frederick Delfin, Ellen Gunnarsdóttir, Manfred Kayser, and Mark Stoneking, Proceedings of the National Academy of Sciences, 

http://www.pnas.org/content/early/2013/01/09/1211927110

Abstract:The Australian continent holds some of the earliest archaeological evidence for the expansion of modern humans out of Africa, with initial occupation at least 40,000 y ago. It is commonly assumed that Australia remained largely isolated following initial colonization, but the genetic history of Australians has not been explored in detail to address this issue. Here, we analyze large-scale genotyping data from aboriginal Australians, New Guineans, island Southeast Asians and Indians. We find an ancient association between Australia, New Guinea, and the Mamanwa (a Negrito group from the Philippines), with divergence times for these groups estimated at 36,000 y ago, and supporting the view that these populations represent the descendants of an early “southern route” migration out of Africa, whereas other populations in the region arrived later by a separate dispersal. We also detect a signal indicative of substantial gene flow between the Indian populations and Australia well before European contact, contrary to the prevailing view that there was no contact between Australia and the rest of the world. We estimate this gene flow to have occurred during the Holocene, 4,230 y ago. This is also approximately when changes in tool technology, food processing, and the dingo appear in the Australian archaeological record, suggesting that these may be related to the migration from India.

BBC reports:

“For a long time, it has been commonly assumed that following the initial colonization, Australia was largely isolated as there wasn’t much evidence of further contact with the outside world,” explained Prof Mark Stoneking, from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

“It is one of the first dispersals of modern humans – and it did seem a bit of a conundrum that people who got there this early would have been so isolated.”

To study the early origins of Australia’s population, the team compared genetic material from Aboriginal Australians with DNA from people in New Guinea, South East Asia and India.

By looking at specific locations, called genetic markers, within the DNA sequences, the researchers were able to track the genes to see who was most closely related to whom.

They found an ancient genetic association between New Guineans and Australians, which dates to about 35,000 to 45,000 years ago. At that time, Australia and New Guinea were a single land mass, called Sahul, and this tallies with the period when the first humans arrived.

But the researchers also found a substantial amount of gene flow between India and Australia.

Prof Stoneking said: “We have a pretty clear signal from looking at a large number of genetic markers from all across the genome that there was contact between India and Australia somewhere around 4,000 to 5,000 years ago.”

He said the genetic data could not establish the route the Indians would have taken to reach the continent, but it was evidence that Australia was not as cut off as had been assumed.

“Our results show that there were indeed people that made a genetic contribution to Australians from India,” Prof Stoneking explained.

The researchers also looked at fossils and other archaeological discoveries that date to this period.

They said changes in tool technology and new animals could possibly be attributed to the new migrants.

Prof Stoneking said: “We don’t have direct evidence of any connection, but it strongly suggestive that microliths, dingo and the movement of people were all connected.”

The origins of counting

November 11, 2012

Before an intelligence can turn to counting it must first have some concept of numbers. When and how did our ancient ancestors  first develop a concept of numbers and then start counting?

What led humans to counting and when?

…  the increasing complexities of co-operation and their requirements for communication was what drove the parallel – and inter-linked – development of speech and numerology starting some 150,000 years ago.

6,000 generations since Out of Africa

February 13, 2012

Lately, I have been delving into the fascinating – but somewhat arcane – fields of paleo-anthropology and genetics and biology and archeology. I find I am constantly trying to create a narrative which hangs together and looking for the little details which can enable me to personalise and identify with the narrative. It is a search for little “hooks” onto which I can hang my “hats” of understanding. And one such “hook” which both anchors and enables my imagination is that when looked at in the perspective of individuals in a particular line of descent, the ancient past is not as intangible and unreachable as it might seem.

from Wikipedia

It is only simple arithmetic but it seems to me quite remarkable that the long journey from the dawn of anatomically modern humans (AMH) some 250,000 years ago, when considered along any particular line of descent, contains not more than some 12,000 individuals. So the right 12,000 names, if I knew them, would suffice to describe all the individuals on any specific line of descent from my origins as an anatomically modern human. Twelve thousand is not so great a number of people. It is less than the population of the little town I live in and it is a number that would be comfortably handled by even quite a small database. I even hear that some people boast more than 12,000 followers on Twitter and others have more than 12,000 “friends” on Facebook! It does not take many minutes to set up an Excel sheet with 12,000 line items, each line then representing one individual on one of my particular lines of descent.

So I have started a new blogsite called 6,000 Generations to provide an outlet for my speculations about individuals from my Ancestral Generations (AG’s).


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