Rewriting human evolution story: No single human origin

_{Denyse O'Leary

July 13, 2018

Human evolution, Intelligent Design}

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From Hannah Devlin at The Guardian

Researchers say it is time to drop the idea that modern humans originated from a single population in a single location

???

Readers, please wear eye protection due to splinters flying from Human Evolution lecterns:

The origins of our species have long been traced to east Africa, where the world’s oldest undisputed Homo sapiens fossils were discovered. About 300,000 years ago, the story went, a group of primitive humans there underwent a series of genetic and cultural shifts that set them on a unique evolutionary path that resulted in everyone alive today.

However, a team of prominent scientists is now calling for a rewriting of this traditional narrative, based on a comprehensive survey of fossil, archaeological and genetic evidence. Instead, the international team argue, the distinctive features that make us human emerged mosaic-like across different populations spanning the entire African continent. Only after tens or hundreds of thousands of years of interbreeding and cultural exchange between these semi-isolated groups, did the fully fledged modern human come into being.More.

One question this version of the tale raises is, why were they all headed in the same direction developmentally? And no apes were? The old, single-origin story did have the virtue of simplicity: One group just happened to develop a mind in the same way that zebras developed stripes. That made the search for the Missing Link simple, even if fruitless.

Now, it would seem, we all have our own missing links. Let’s see how this version plays out.

See also: Miller: The evidence shows that Lucy is an ape species, not a human ancestor

Comments

GUN Ok, I hadn't even bothered to read what they were saying, so going back - yes, you seem to be correct. However ...
And so what they’re saying is hardly radical, and not new. But I wouldn’t say it isn’t interesting – and it is controversial. As I mention above, it’s contentious as to how much interbreeding and contact was going on within the various African tribes. Some would say that we (as in modern H. sapiens) came from a single population, or a few, or that there was gene flow across the continent (or even beyond).
I don't see what is important, interesting or even controversial about it. The single-origin story stands. "Non-humans" evolved into early-humans, supposedly (this story does not touch on that) - all from a single origin. The only "rewrite" that is involved is how the early-human homo sapiens (all the same species) were separated. The common view is as the report says:
Previously, this has either been explained as evidence of a single, large population trekking around the continent en masse or by dismissing certain fossils as side-branches of the modern human lineage that just happened to have developed certain anatomical similarities.
Ok, where it says "just happened to have developed certain anatomical similarities" -- they usually call that convergent evolution. That was one idea, and there are all sorts of explanations about "predisposition to evolve" certain similar features independently, etc. But I will accept the first point as the more common 'previous' view. A single-origin of this species, then travelled across Africa. The new, supposedly radical idea (and it does not seem to be) is this:
The latest analysis suggests that this patchwork emergence of human traits can be explained by the existence of multiple populations that were periodically separated for millennia by rivers, deserts, forests and mountains before coming into contact again due to shifts in the climate.
So, the old idea said the single origin species travelled across Africa. The new idea says that the single-origin species were separated by geographical changes (new rivers). Then supposedly, they came back together, inter-bred and shared characteristics. Both are single-origin stories. To me, there is nothing interesting here. It's just more evolutionary speculation. It makes no difference. Except, we did notice that someone (whoever) claimed that features evolved convergently across Africa. I would say, "why not"? That's the story of convergent evolution of other species, why not of several pre-human species in Africa? They just all "happened to have the same mutational and selection pathways" and non-humans became human. It's also easy for me to forget that evolutionists believe that the difference between humans and non-human animals is one entirely of physical characteristics. The belief is that rationality and consciousness are reducible to mutations in DNA (and also that consciousness can be detected from fossil evidence). I find that idea to be absurd. But a lot of people believe is, so there's not much I can say at this point.Silver Asiatic_{July 15, 2018
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SA,
Well, the story seems to be about the origin of human beings, but then it says “interbreeding” which means they already were the same species.
Well, they agree - they classify all the groups they discuss as "Homo sapiens." Some of the language they use is a bit vague (perhaps purposely trying to avoid the controversy as to what's a "species") but, suffice to say, they are talking about very closely related populations fully capable of interbreeding. As the story describes it, this is describing how we went from "early Homo sapiens" to the "fully fledged modern human." For instance, from the story:
The telltale characteristics of a modern human – globular brain case, a chin, a more delicate brow and a small face – seem to first appear in different places at different times.
But they also describe the populations from those different places and times as H. sapiens.
As above, I think when we talk about ancestor we are talking about the change of one species into another. That’s the evolutionary story.
Not necessarily.
It’s not a question of changes in the same species through interbreeding. The evolutionary ancestor is a different species, so in this case, it is a question of the origin of all of these interbreeding tribes.
How a species changes over time is also part of evolution.
Usually the explanation is convergent evolution. Pre-human species evolved the same characteristics independently that enabled them to interbreed.
Usually the explanation is convergent evolution? What? Can you give an example of convergent evolution that resulted in that kind of thing? I've never heard of this idea before.
Otherwise, if they’re saying all of the pre-humans evolved from the same ancestors and then scattered across the entire continent of Africa (and then joined again to interbreed) — then that is simply the single-origin theory and not a rewrite of it.
Replace "pre-humans" with "pre-modern humans", then that is pretty much what they are saying. And so what they're saying is hardly radical, and not new. But I wouldn't say it isn't interesting - and it is controversial. As I mention above, it's contentious as to how much interbreeding and contact was going on within the various African tribes. Some would say that we (as in modern H. sapiens) came from a single population, or a few, or that there was gene flow across the continent (or even beyond). It's kinda like if someone argued that Native Americans came from a particular ancient Asian population because the population has character "A" like Native Americans, while someone else thinks that instead another population is the ancestor of Native Americans because they have characteristic "B" like Native Americans. Then someone else proposes that the two populations came into contact and interbred and that's what produced Native Americans. Not only is there no convergent evolution here, it would actually be a rival theory. Those that propose that the Native Americans came from the first population would likely propose that the reason that the latter population has character "B" like the Native Americans is because of convergent evolution, and vice versa.goodusername_{July 15, 2018
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GUN
They’re proposing that different tribes each had their own different mutations and selection pressures, and then through merging/interbreeding, tribes exchanged and picked up characteristics from other tribes.
Well, the story seems to be about the origin of human beings, but then it says "interbreeding" which means they already were the same species. They became that species from some non-common ancestral species. So, they either had the same mutations creating the same features as other "tribes" -- or they had different mutations that created the same features, enabling them to interbreed.
Say you have a tribe of Homo sapiens with characteristic ‘A’, another tribe with characteristic ‘B’, and another with characteristic ‘C’, and each of those characteristics are associated with modern humans – which tribe is an ancestor? Tribes merge, split up, and interbreed, etc, so does it make sense to say that any one of the tribes is an ancestor? Sometimes you have different populations like this with paleontologists arguing over which population is our ancestor.
As above, I think when we talk about ancestor we are talking about the change of one species into another. That's the evolutionary story. It's not a question of changes in the same species through interbreeding. The evolutionary ancestor is a different species, so in this case, it is a question of the origin of all of these interbreeding tribes. Usually the explanation is convergent evolution. Pre-human species evolved the same characteristics independently that enabled them to interbreed. Otherwise, if they're saying all of the pre-humans evolved from the same ancestors and then scattered across the entire continent of Africa (and then joined again to interbreed) -- then that is simply the single-origin theory and not a rewrite of it.Silver Asiatic_{July 14, 2018
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Exactly. We’re supposed to believe that dozens of tribes had the same mutations and selection pressures, independently, at thousands of miles separation and made the transition from non-rational animal to human in the same way.
That's, literally, the very opposite of what they're proposing. They're proposing that different tribes each had their own different mutations and selection pressures, and then through merging/interbreeding, tribes exchanged and picked up characteristics from other tribes. Say you have a tribe of Homo sapiens with characteristic 'A', another tribe with characteristic 'B', and another with characteristic 'C', and each of those characteristics are associated with modern humans - which tribe is an ancestor? Tribes merge, split up, and interbreed, etc, so does it make sense to say that any one of the tribes is an ancestor? Sometimes you have different populations like this with paleontologists arguing over which population is our ancestor. It's always been believed that interbreeding is part of the story - although it's contentious as to how much of it occurred. It's also contentious as to what constitutes a "population" in this case - some would argue that "Africa" was a population. So it's partly an argument of semantics.goodusername_{July 14, 2018
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vmahuna
So these dozens of INDEPENDENT tribes each developed tools and a spoken language and weird haircuts and proper etiquette for nose-picking by themselves? Maybe there are genes for that.
Exactly. We're supposed to believe that dozens of tribes had the same mutations and selection pressures, independently, at thousands of miles separation and made the transition from non-rational animal to human in the same way. This, along with the difficulty of explaining why any animals needed the brain size and power that humans have.
My guess is that the “experts” are caught in a position where the newest factoids simply don’t work with the old general explanations.
I see it that way. Over the past decade these little reports of "new origin sites" emerged - across Africa, and some from Asia. These have just been ignored. Eventually, now someone thinks it is safe enough to rewrite the story. All they have is the contradictory findings. Bringing it together into a new evolutionary scheme just requires imagination and story-telling skills.
So they invent a new general explanation that makes even less sense than the old one. And we’re supposed to respect their wild guesses because…
That's it. The new 'explanation' has more problems than the old one. Plus, it's obvious that they just invented this out of nothing. These scientists apparently never encounter anyone who actually challenges their faith-based ideas. So,they feel free to just make up any story they want and everyone around them just nods their heads: "Yes, interesting new idea. That's how science works. We can just rewrite scientific theories at a moment's notice. We do it all the time - like Einstein did with Newton. Here's just another example. This proves why evolution is true." They start with their faith-belief "animals evolved into humans". Then, anything that is observed in nature is just made to fit the belief.Silver Asiatic_{July 14, 2018
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Well, once merged they’re at the same point.
Ok, sure, why not? The traditional narrative was a single-origin story. This new idea says that there were multiple origins spanning the entire continent. In both cases, we had non-human animals, and then some of them became human. How it actually happened, clearly, is not the important part of the story. The important part is that non-human animals somehow became human and here we are today. The fact that you can act as if there is no problem to the "rewriting" of the traditional narrative and adopt a tone of: "of course, that's the point" - as I perceive it, means you'd accept any re-write of the Darwinian story, including a complete dismissal of mutations and selection - as long as some evolutionary narrative remains in place. I find that to be a faith-based position that will easily fit any contradictory facts into a story-line, merely through use of speculation, imagination and conjecture. But why should anyone take that seriously? Why were we required to believe that the traditional narrative of human origins was something that could not be doubted or "rewritten"?Silver Asiatic_{July 14, 2018
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I'll work up some other questions, but how does this "multiple site development" thing work if the MINIMUM required human population (for EACH isolated pack/clan/tribe) MUST be 10,000 or more individuals? I'm also guessing that the 10,000 are the sexually mature portion of each pack/clan/tribe, and the Demographics guys tell us as a certain FACT that in "primitive" cultures, 50% of the population is below the age of 12 or 14 (i.e., sexually immature). So these dozens of INDEPENDENT tribes each developed tools and a spoken language and weird haircuts and proper etiquette for nose-picking by themselves? Maybe there are genes for that. My guess is that the "experts" are caught in a position where the newest factoids simply don't work with the old general explanations. So they invent a new general explanation that makes even less sense than the old one. And we're supposed to respect their wild guesses because...vmahuna_{July 13, 2018
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SA,
They were going in different directions but all ended up at the same endpoint?
Well, once merged they're at the same point.goodusername_{July 13, 2018
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asauber
Seriously, what’s the difference if they did or not as far as Evolution is concerned?
That seems to be the key point in any evolutionary report. "It doesn't matter what we find, or how we have to 're-write' the narrative, we will always find a story to make it seem like we know what we're talking about and that evolution is the reason for everything."Silver Asiatic_{July 13, 2018
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GUN
They weren’t. That’s the point. Different populations were diverging and going in different directions, developing differently, but then various populations merge again combining various characteristics, and so on.
They were going in different directions but all ended up at the same endpoint?Silver Asiatic_{July 13, 2018
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time to drop the idea modern humans originated in a single population in a single location
Seriously, what's the difference if they did or not as far as Evolution is concerned? Is this the Evolutionary Fairly Tale searching for greater believability? You bet. Andrewasauber_{July 13, 2018
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One question this version of the tale raises is, why were they all headed in the same direction developmentally?
They weren't. That's the point. Different populations were diverging and going in different directions, developing differently, but then various populations merge again combining various characteristics, and so on.goodusername_{July 13, 2018
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