Rethinking our human origins in Africa | Hacker News Reader

Rethinking our human origins in Africa

nhm.ac.uk

91 pointsXzetaU831 comments

"Ancient H. sapiens appear to have been even more physically diverse than the world's populations are today, which doesn’t fit with the idea that they all started from one small group."

I believe that the theory they're supposed to be debunking is not that the old (>300,000 yrs) sapiens population descended from a single regional population. The theory is that by 300k ybp there was a divverse sapiens population in and near Africa. They had a wider range of physical appearance than modern humans. Our ancestors descended from a sub-population of archaic sapiens (before mixing with other homo species).

The theory explains why we're so much more homogeneous than very old sapiens who still sometimes exhibited "primitive" (isn't this a truism?) skull shapes and such. We went through a bottleneck at some point.

IE, many flavours of sapiens existed. We descend from one of them. The Morocco & Levant sapiens have no descendants.

> A new paper challenges the traditional idea that our species evolved from a single population in one region of Africa.

every article or paper on this topic in the last 10 years talked about a complicated network of genetic branches instead of a simple linear tree

In fairness...

>a complicated network of genetic branches...

kind of implies a tree.

I haven't read the other papers, but, at it's root, the paper that is the subject of this posting seems to imply that the root species came much, much earlier than we typically believe. I'd need more access to the genetic data they are basing that conclusion on to know if they are right? But it sounds right. Why could sapiens not have risen in Africa millions of years earlier? (At the same time, we have to be careful. Sounding right is not how we should be evaluating scientific theories.)

> In fairness...
> >a complicated network of genetic branches...

> kind of implies a tree.

Not quite. The implication is that some separate branches that developed distinct (but not incompatible) differences over time due to geographical or social separation later merged into other branches, meaning that there isn't a simple linear sequence from every point in the tree back to the one root.

Exactly. I have heard the expression "braided stream" be used for this description.

Yes! Neanderthals being the most prominent recent example.

Now let's convince linguists that Semitic and PIE languages are related and we have won!

This makes a lot more sense to me. Whenever I see a description of a long period of history as being mainly static, such as humans evolving as a separate group within Africa for a hundred thousand years or more, it sets off alarm bells. It just sounds like historians and archaeologists only have a few reference points to work from so they extrapolate between them in a straight line or a nice smooth curve. Real human history is messy, complicated and often violent.

I'm not getting at the science or it's practitioners, they can't just make up complex changes without evidence, but let's be honest that any such seemingly static periods of history due to limited evidence are probably just placeholder theories for whatever was actually happening.

This reminds me of the so-called "dark ages". Bronze age collapse, Middle ages…

Early historians used to call them dark because of just such "limited evidence". Little surviving records, compared to the periods before/after.

But these "periods of silence" may have given us something less tangible but even more lasting than literature and architecture. The fabric of societies was rewoven, new modes of thinking and organization emerged from the chaos. People may not have been into books and stone, but they were certainly not idle!

The inhales and exhales at the scale of humanity are sometimes hard to appreciate, or even tell apart, from our individual level.

The common notion is that there wasn't much technological development going on. Stone tools, hunting gathering for a long time, then civilization over the last 10.00 years. Your point still applies to a degree, but it's amazing what they can already tell from the remains that didn't fall to the forces of nature.

The observation that humans (originally human females) descended from a woman who lived about 240,000 years ago in Africa was first demonstrated by Allan C. Wilson, who looked at the evolution of mitochondrial DNA sequences, in 1987.

This was a very controversial result, in part because the length of human history was so young (much less than the 1 million years that some fossils suggested), and because the origin was placed in Africa. Shortly after this, I heard Wilson discuss the controversy, and he remarked that he was surprised that there was so much disagreement about the idea that a set of genes in a population could be attributed to a single individual. He pointed out that this was well understood by population biologists in the early 20th century; basically, for any population of individuals at some time in the past, after a long enough time, the descendants of that population will have genes that can be traced back to one individual -- that one individual whose children had children who had children ... Though well established in 1987 (and decades earlier), but it was still argued about (and apparently still is).

Mitochondrial DNA can be traced back to an individual Africa (mitochondrial eve), less than 300,000 years ago.

> controversial result, in part because the length

This part doesn't make sense. The controversy must have been a misunderstanding. 'mt-MRCA' is a moving target. It is the most recent common ancestor (MRCA) of the currently living population. The mt-MRCA for the population earlier in time would be older than the current mt-MRCA. Similarly for Y-MRCA.

Interesting.

In the early aughts, my TA in University was writing a similar paper for his doctoral degree. All of the professors in the department said it was good enough to be a PhD paper.

His premise was there were several divergent populations not only in Africa, but in Nordic regions and Eastern Europe from where we evolved from.

It's cool to see this shift in the dominant paradigm is finally starting to shift, some 20 years after my TA (and presumably many others) proposed it.

Nice to see academic researchers are now trying to utilize a more phenomenological approach in their theorizing. Ideally, What does the available data strongly suggest? should be in the forefront rather than group conformity to some conditioned or ingrained ethnic or anti-ethnic grounded chauvinistic penchants. Time to grow up :)

Nah! The problem in the first place is to wonder where to find any data at all and in the last twenty years new data has become available. It's a back and forth, really.

The summary doesn't seem to mention the idea that there may have been one or more population bottlenecks between the emergence of H. sapiens and now.

A neanderthal skull juxtaposed with one from a human shows the more-primitive elongated shape mentioned in the article or primitive human species:

public.media.smithsonianmag.com/legacy_blog/skulls.jpg

To me it is fascinating to imagine what this species was like with their larger brains, but smaller frontal lobes, which are believed to have been more-focused on their senses and athleticism.

Just curious, why is this being grey’d?

Probably because this talk of skull-shape and less intelligence sounds a lot like phrenology - an old psuedoscience used to determine the latent abilities of a person, based on their skull shape. Which ultimately was related to their race - and used to look down upon different people groups.

Once you believe there is a strong causation between skull shape and intelligence, the racist conclusions write themselves.

I assume good faith on the part of the GP, though.

I've read a bit about them and most sources say this, 'they were more encephalized and even in absolute terms had larger brains, but probably were not more intelligent.'

I didn't have any idea anyone would interpret this as racist, wtf?

The discussion on skull evolution I reference here is also mentioned in the OP. How can I be accused of racism and not the OP? That isn't consistent.

Ha! Pump your breaks tiger; no one is accusing you of racism, people are makimg the observation that some could make that interpretation, amd such interpretations have a marked history in America.

Don't get hostile or defensive over a misunderstanding, please.

Well if you know your american history, it was used as yet another rationale to disparage afroamericans

Interestingly, Gould's "debunking" turned out to be fraudulent: https://www.nytimes.com/2011/06/14/science/14skull.html

I don't know much about these researchers but I'm sure their research will be used by those who believe ridiculous things like this and will definitely use it to drive their own racist narratives. You can count on that happening.

HN downvotes are kind of random sometimes. Upvote if you don't like it. :)

I know some people who would use this research to try and argue that humans of different races are in fact more separate genetically than is popularly believed. Does this research suggest anything of the sort?

No.

No. However, I am certain that there will be others that will try. You can count on it.

If you're interested in the ancient DNA, I highly recommend "Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past" by David Reich.

It's been obvious for a while now, that the out of Africa theory was far too simplistic.

Denisovan DNA for instance, of which there is no sign in any African and very few European people...

Except the article still says its out of Africa, just not from a single region in Africa.

Homo sapiens evolved within African, from several apparently separate and only occasionally intermixing populations.

My intuition is that something extremely similar happened for Neanderthals in Europe and Denisovans in Asia.

After speciating, Denisovans and Neanderthals migrated at least within Eurasia, and those populations intermixed.

At least as early as that was happening, Homo sapiens started migrating out of Africa, and intermixed with the Homo genus populations they encountered. At some later point, distinctly Neanderthal, Denisovan, and Neanderthal/Denisovan populations apparently died off.

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