Recent Exciting Developments: 130kya American Hominins?

There has been SO MUCH EXCITING NEWS out of paleoanthropology/genetics lately, it’s been a little tricky keeping up with it all. I’ve been holding off on commenting on some of the recent developments to give myself time to think them over, but here goes:

  1. Ancient hominins in the US?
  2. Homo naledi
  3. Homo flores
  4. Humans evolved in Europe?
  5. In two days, first H Sap was pushed back to 260,000 years,
  6. then to 300,000 years!
  7. Bell beaker paper

1. Back in May (2017,) Holen et al published an article discussing A 130,000-year-old archaeological site in southern California, USA, in Nature:

Here we describe the Cerutti Mastodon (CM) site, an archaeological site from the early late Pleistocene epoch, where in situ hammerstones and stone anvils occur in spatio-temporal association with fragmentary remains of a single mastodon (Mammut americanum). The CM site contains spiral-fractured bone and molar fragments, indicating that breakage occured while fresh. Several of these fragments also preserve evidence of percussion. The occurrence and distribution of bone, molar and stone refits suggest that breakage occurred at the site of burial. Five large cobbles (hammerstones and anvils) in the CM bone bed display use-wear and impact marks, and are hydraulically anomalous relative to the low-energy context of the enclosing sandy silt stratum. 230Th/U radiometric analysis of multiple bone specimens using diffusion–adsorption–decay dating models indicates a burial date of 130.7 ± 9.4 thousand years ago. These findings confirm the presence of an unidentified species of Homo at the CM site during the last interglacial period (MIS 5e; early late Pleistocene), indicating that humans with manual dexterity and the experiential knowledge to use hammerstones and anvils processed mastodon limb bones for marrow extraction and/or raw material for tool production.

Reconstruction of a Homo erectus woman, Smithsonian

Note that “Homo” here is probably not H. sapiens, but a related or ancestral species, like Denisovans or Homo erectus, because as far as we know, H. sapiens was still living in Africa at the time.

This is obviously a highly controversial claim. Heck, “earliest human presence in the Americas” was already controversial, with some folks firmly camped at 15,000 years ago and others camped around 40,000 yeas ago. 130,000 years ago wasn’t even on the table.

Unfortunately, the article is paywalled, so I can’t read the whole thing and answer simple questions like, “Did they test the thickness of mineral accumulation on the bones to see if the breaks/scratches are the same age as the bones themselves?” That is, minerals build up on the surfaces of old bones over time. If the breaks and scratches were made before the bones were buried, they’ll have the same amount of buildup as the rest of the bone surfaces. If the breaks are more recent–say, the result of a bulldozer accidentally backing over the bones–they won’t.

They did get an actual elephant skeleton and smacked it with rocks to see if it would break in the same ways as the mammoth skeleton. A truck rolling over a rib and a rock striking it at an angle are bound to produce different kinds and patterns of breakage (the truck is likely to do more crushing, the rock to leave percussive impacts.) I’d also like to know if they compared the overall butchering pattern to known stone-tool-butchered elephants or mammoths, although I don’t know how easy it would be to find one.

Oldowan tool, about 2 million years old

They also looked at the pattern of impacts and shapes of the “hammerstones.” A rock which has been modified by humans hitting it with another rock will typically have certain shapes and patterns on its surface that can tell you things like which angle the rock was struck from during crafting. I’ve found a few arrowheads, and they are pretty distinct from other rocks.

Here’s a picture of an Oldowan stone chopper, about 2 million years old, which is therefore far older than these potential 130,000 year old tools. Homo sapiens didn’t exist 2 million years ago; this pointy rock was probably wielded by species such as Australopithecus garhi, H. habilis, or H. ergaster. Note that one side of this chopper is rounded, intended for holding comfortably in your hand, while the other side has had several chunks of rock smacked off, resulting in convex surfaces. Often you can tel exactly where the stone tool was struck to remove a flake, based on the shape and angle of the surface and the pattern of concentric, circular lines radiating out from the impact spot.

Homo erectus, who lived after the Oldowan tool makers and had a fancier, more complicated lithic technology, did make it out of Africa and spread across southeast Asia, up into China. This is, as far as I know, the first case of a hominin species using tools to significantly expand its range, but we have no evidence of erectus ever expanding into places that get significantly cold in the winter, and boat-building is a pretty advanced skill. We don’t even think erectus made it to Madagascar, which makes it sailing to the Americans rather doubtful.

I dislike passing judgment on the paper without reading it, but my basic instinct is skepticism. While I think the peopling of the Americas will ultimately turn out to be a longer, more complex, and interesting process than the 15,000 years camp, 130,000 years is just too interesting a claim to believe without further evidence (like the bones of said hominins.)

Still, I keep an open mind and await new findings.

(We’ll continue with part 2 next week.)

Where are the Ethnic Groups on Haak’s Graph?

Click for full size

Do you ever take a look at Haak et al’s wonderful graph of admixture in different human ethnic groups and wonder where, exactly, the Tlingit or Inga are from?

americasI certainly have, so I’ve been working on this handy map that shows the location of each group (except for the Surui, because apparently there are two groups called the Surui, and I haven’t determined yet which is in the dataset, but they’re both in Brazil.)

Note also that the Chipewyans, Algonquins, Ojibwe, and Cree all have very large ranges; I have only been able to approximate their locations.

Today I finished the Americas; tomorrow I’ll start work on the rest of the world.

In the grand human family tree, all of these American groups are on the “Asian” branch, but most of them split off from the other Asians long ago (the Inuit, Aleuts, and Tlingit appear to have arrived more recently in the New World and be closely related to various groups in Siberia.)

I’ve gone into the details of the groups before, so I won’t bore you by rehashing them now.

Note also I did not use Haak et al’s full graph, but a very cropped version. I tried using the full thing, but it was horribly unwieldy.

Haak et al’s full graph

WARNING: This post is full of speculations that I am recording for my own sake but are highly likely to be wrong!

Click for full size
From Haak et al.

Hey, did you know that this isn’t actually Haak et al’s full DNA graph? The actual full dataset looks like this:

 

Picture 1Picture 2

 

 

 

 

 

 

Isn’t it beautiful?

You’re going to have to click for the full size–sorry I couldn’t fit it all into one screen cap. I’m also sorry that the resolution is poor, and therefore you can’t read the labels (though you should be able to figure out which is which if you just compare with the smaller graphic at the top of the screen. (Supposedly there’s a higher resolution version of this out there, but I couldn’t find it.)

Why the reliance on a greatly cropped image? Just the obvious: the big one is unwieldy, and most of the data people are interested in is at the top.

But the data at the bottom is interesting, too.

On the lefthand side of the graph, we have a measure of granularity–how much fine detail we are getting with our genetic data. The bottom row, therefore, shows us the largest genetic splits between groups–presumably, the oldest splits.

From left to right, we have selections of different ethnic groups’ DNA. Old European skeletons constitute the first group; the mostly pink with some brown section is Native North/South American; the blue and green section is African; the big wide orange section is mostly European and Middle Eastern; then we have some kind of random groups like the Inuit (gold), Onge (pink, Indian Ocean), and Australian Aborigines; the heavily green areas are India; the mixed-up area splitting the green is Eurasian steppe; the yellow area is East Asian; and the final section is Siberian.

Level One: Sub-Saharan Africa (SSA) vs. Non-Sub-Saharan Africa

The bottom row shows us, presumably, the oldest split, between the orange and the blue. All of these light blue groups, from the Ju Hoan (Bushmen/San) to the Yoruba (Nigeria,) Somalis to Hadza (Tanzania,) African Americans to Shua (Khoe speakers of Namibia/Botswana,) are from Africa–sub-Saharan Africa, I’d wager (though I’m not sure whether Ethiopia and Somalia are considered “sub-Saharan.”)

All of the other groups–including the sampled north-African groups like Saharawari (from Western Sahara,) Tunisians, Algerians, Mozabites (Algeria,) and Egyptians–show up in orange.

(Note: Light green and orange are completely arbitrary color choices used to represent the DNA in these graphs; there is nothing inherently “orange” or “green” or any other color about DNA.)

I would not actually have predicted this–other studies I have read predicted that the split between the Bushmen, Pygmies, and other groups in Africa went back further in Africa than the split between Africans and non-Africans, but perhaps the Sahara has been the most significant barrier in human history.

Interestingly, the split is not absolute–there are Sub-Saharan groups with non-SSA admixture, and non-SSA groups with SSA admixture. In fact, most of the SSA groups sampled appear to have some non-SSA admixture, which probably has something to do with back-migration over the centuries; predictably, this is highest in places like Somalia and Ethiopia, fairly high along the east coast of Africa (which has historically been linked via monsoon trade routes to other, non-African countries;) and in African Americans (whose admixture is much more recent.) (Likewise, the admixture found in some of the hunter-gatherer peoples of southern Africa could be relatively recent.)

The Non-SSA groups with the most SSA admixture, are north African groups like the aforementioned Algerians and Tunisians; Middle Eastern groups like the Druze, Syrians, Bedouins, Jordanians, etc.; “Mediterranean” groups like the Sicilians and Maltese; various Jewish groups that live in these areas; and a tiny bit that shows up in the people of the Andaman Islands, Australia, and PNG.

(Oh, and in various old European skeletons.)

Level Two: “Western” vs. “Eastern”

Moving on to level two, we have the next big split, between “Easterners” (mostly Asians) and “Westerners” (mostly Europeans and Middle-Easterners.)

Natives of North/South America, Inuits, Andaman Islanders, Australian Aborigines, Papuans, the Kharia (an Indian tribe that has historically spoken a non-Indo-European language,) some central or northern Asian steppe peoples like the Evens (Siberians,) and of course everyone from the Kusunda (Nepal) through China and Japan and up through, well, more Siberians like the Yakuts, all show up as mostly yellow.

Everyone from Europe, the Middle East, the Caucuses, and all of the sampled Indian populations except the Kharia have orange.

A bunch of little groups from the middle of Eurasia show up as about half-and-half.

Interestingly, some of the older European hunter-gatherer skeletons have small quantities of “Eastern” DNA; this may not represent admixture so much as common ancestry. It also shows up, predictably, in Turkey and the Caucuses; in Russia/Finns; tiny quantities in places like the Ukraine; and quite significantly in India.

Significant “Western” admixture shows up in various Natives North/South Americans (probably due to recent admixture,) the Andaman Islands, Aborigines, PNG, (this may represent something to do with a common ancestor rather than admixture, per se,) and Siberia.

Level Three: Native North/South Americans vs. “Easterners”

At this point, the “light pink” shows up in all of the sampled indigenous tribes of North and South America. A fair amount of it also shows up in the Inuit, and a small quantity in various Siberian tribes. A tiny quantity also show up in some of the older European skeletons (I suspect this is due to older skeletons being more similar to the common ancestors before the splits than trans-Atlantic contact in the stone age, but it could also be due to a small Siberian component having made its way into Europe.)

Even at this level, there is a big difference evident between the groups from Central and South America (almost pure pink) and those from northern North America, (significant chunk of orange.) Some (or all) of that may be due to recent admixture due to adoption of and intermarrying with whites, but some could also be due to the ancestors of the Chipewyans etc. having started out with more, due to sharing ancestors from a more recent migration across the Bering Strait. I’m speculating, of course.

Level Four: Intra-African splits

I don’t know my African ethnic groups like I ought to, but basically we have the Bushmen (aka San,) and I think some Khoe / Khoi peoples in green, with a fair amount of green also showing up in the Pygmies and other hunter-gatherers like the Hadza, plus little bits showing up in groups like the Sandawe and South African Bantus.

Level Five: Australian Aborigines, PNG, and Andamanese split off.

Some of this DNA is shared with folks in India; a tiny bit shows up in central Asia and even east Asia.

Level Six: Red shows up.

This reddish DNA is found in all “Siberian” peoples, people who might have moved recently through Siberia, and people who might be related to or had contact with them. It’s found throughout East Asia, eg, Japan and China, but only found in high quantities among the Inuit and various Siberian groups. At this resolution, oddly, no one–except almost the Itelmen and Koryak–is pure reddish, but at higher resolutions the Nganasan are, while the Itelmen and Koryak aren’t.

Level Seven: The “Indos” of the Indo-Europeans show up

Although no pure light green people have yet been found, their DNA shows up everywhere the Indo-Europeans (aka Yamnaya) went, with their highest concentration in India. Perhaps the light green people got their start in India, and later a group of them merged with the dark blue people to become the Yamnaya, a group of whom then migrated back into India, leaving India with a particularly high % of light green DNA even before the dark blue shows up.

Interestingly, some of this light green also show up in the Andamanese.

Level Eight: The “Europeans” of the Indo-Europeans show up

The dark blue color originates, in the left-hand side of the graph, with a several-thousand years old population of European hunter-gatherers which, as you can see in the slightly younger populations on the far left, nearly got wiped out by a nearly pure orange population of farmers that migrated into Europe from the Middle East. This dark blue population managed to survive out on the Eurasian Steppe, which wasn’t so suited to farming, where it merged with the light-green people. They became the Yamnaya aka the Indo-Europeans. They then spread back into Europe, the Middle East, India, central Asia, and Siberia. (The dark blue in modern Native American populations is probably due to recent admixture.)

Level Nine: The Hadza

The Hadza (a hunter-gatherer people of Tanzania) now show up as bright pink. No one else has a lot of bright pink, but the Pygmies (Mbutu and Biaka,) as well as a variety of other eastern-African groups located near them, like the Luo, Masai, and the Somalis have small amounts.

Level Ten: The Onge (Andamanese)

Not much happens here, but the Onge (from the Andaman Islands) turn peach and stay that way. It looks like a small amount of peach DNA may also be found across part of India (southern India, I’m assuming.)

Level Eleven: Chipewyans (North America)

The Chipewyans turn brown; brown is also found in small quantities in Central America, in moderate quantities in eastern North America, and in the Eskimo/Inuit.

Level Twelve: Pygmies

The Biaka and Mbuti Pygmies differentiate from their neighbors. Tiny quantities of Pygmy DNA found in probably-nearby peoples.

Level Thirteen: Inuit/Eskimo

They become distinctly differentiated from other North American or Siberian tribes (olive green.), Their olive green shade is found in small quantities in some Siberian tribes, but interestingly, appears to be totally absent from other Native American tribes.

Level Fourteen: Horn of Africa

A dusty peach tone is used for groups in the Horn of Africa like the Somalis and Ethiopians, as well as nearby groups like the Dinka. Small amounts of dusty peach are are also found along the East Africa, North Africa, and the Middle East. Smaller amounts appear to be in a variety of other groups related to the Bushmen.

Level Fifteen: The light green turns teal

All of the light green in Europe turns teal, but much of the light green in India stays light green. (Teal also shows up in India.) I have no idea why, other than my aforementioned theory that India had more light green to start with.

Level Sixteen: Amazon Rainforest tribes

The Kuritiana and Suri show up in light olive; light olive is also found in small quantities in other parts of Central and South America, and tiny bits in parts of North America, and maybe tiny amounts in the Eskimo but I don’t see any in the Chukchi, Itelmen, etc.

Level Seventeen: Bedouins

The Bedouins turn light purple; this DNA is also found through out the Middle East, Turkey, North Africa, the Mediterranean (eg Sicily), Greece, Albania, Spain, Bulgaria, Ashkenazim, and a tiny bit In India.

Level Eighteen: Some Bushmen appear to split off from some other Bushmen.

I don’t know much about these groups.

Level Nineteen: Nothing interesting appears to happen.

Please remember that all of this is me speculating. I am definitely not an educated source on these matters, but I hope you’ve had as much fun as I’ve had peering at the DNA and thinking about how people might have moved around and mixed and split to make the colors.