A recent toast to James Watson highlights a tolerance for bigotry many want excised from the scientific community.
A hominin skull found in Dmanisi reveals that human ancestors migrating from Africa were more primitive than once thought.
October 17, 2013|
GEORGIAN NATIONAL MUSEUMScientists have unearthed the first ever completely preserved skull of an adult hominin from the Paleolithic era—spanning approximately 2.6 million to 10,000 years ago. The specimen, described in a paper published online today (October 17) in Science, together with other skull specimens found at the same site in Dmanisi, Georgia, indicate that the early evolving lineage of Homo was still relatively primitive when it left Africa, and also that it exhibited considerable variation between members of the same species.
“This is going to be a classic paper in paleoanthropology,” said Tim White, a professor at the University of California, Berkeley, who was not involved in the work. “The reason for that is not so much the cranium itself . . . but rather the entire package of evidence from this locality,” he said. The new skull is clearly the cherry on the cake, however, because it is “spectacularly complete,” said White. “It’s an amazing skull,” added Robert Foley, a professor of human evolution at the University of Cambridge, who also was not involved in the work. “Just a fantastic specimen.”
The jaw of the skull was found in 2000. Its matching cranium was discovered five years later. It was easy to tell the parts were from the same individual, however, because “the teeth match with each other,” said Christoph Zollikofer, a professor at the Anthropological Institute at the University of Zurich, who led the study. “They are like fingerprints,” he said.
Other Homo skulls have been found before, but have been damaged, incomplete, or had other problems “that prevented paleoanthropologists from knowing how a normal adult skull of an early Homo would look,” said Zollikofer. For example, two other well-preserved skulls were also found at the Dmanisi site, but one was from an adolescent and the other was elderly. “In juveniles, the face still has to grow quite a bit,” explained Zollikofer, while the elderly specimen’s jaw morphology had been strongly altered by bone resorption following loss of the teeth.
“That’s the very special thing about [the new skull]: everything is there, every tooth is preserved, all the minutest details of the morphology are there,” Zollikofer said.
Based on the features of the skull, it is thought to have been a male with large cheek bones, teeth, and jaws, but a small brain. “It was really interesting to see this specific combination of a small brain and a big face,” said Zollikofer, “because this is something that has never been found [before].” Indeed, fossils of big jaw bones and small craniums would previously have been assigned to different Homo species, he said. “Now we see it clearly in one single individual.”
The other striking indication about the small brain is that, contrary to previous consensus, it suggests “it was not expansion of the brain that allowed [Homo’s] geographic expansion in range,” said White. “What the Dmanisi material is showing us is that the first hominins out of Africa . . . were clearly very early in the lineage,” said Foley.
The newly described skull also expands the morphological variability of the specimens found at the Dmanisi site—some of which appear less primitive. Despite this variability, Zollikofer believes all the specimens are members of the same species. That would be “the most parsimonious explanation,” agreed Foley, because the remains were deposited together in one place at one time.
In support of the single species theory, Zollikofer found that the morphological variability within the Dmanisi specimens was in fact no more than that found in modern humans, or chimps, or bonobos. He suggested that other hominin fossils previously classified as separate species—such as H. habilis, H. rudolfensis, and H. erectus—should be re-examined.
“We urge for a change in perspective, because what has happened in the last ten years is that people tried to divide—they tried to show species diversity—and what we try to show now is diversity, but within one single evolving species,” Zollikofer said.
D. Lordkipanidze et al., “A complete skull from Dmanisi, Georgia, and the evolutionary biology of early Homo,” Science, 342: 326-331, 2013.
October 18, 2013
The single species theory takes the disarray from mutation-initiated natural selection and replaces it with nutrient-dependent ecological niche construction and pheromone-controlled social niche construction (via the metabolism of nutrients to species-specific pheromones). Pheromones control the physiology of reproduction, which is how they control nutrient-dependent adaptive evolution sans mutations.
Anyone willing stop thinking in terms of mutation-driven evolution should quickly realize that the single species theory integrates findings from Skull 5, and that those findings are consistent with what is already known about nutrient-dependent pheromone-controlled adaptive evolution via ecological, social, neurogenic, and socio-cognitive niche construction exemplified in species from microbes to man.
The complete skull that brings natural variations across 2.8 million to 10,000 years also links the more recent changes in our genome to the nutrient-dependent pheromone-controlled alternative splicings that made us modern humans, in the context of findings that confirm earlier work "...suggesting that the majority of variants, including potentially harmful ones, were picked up during the past 5,000–10,000 years."
See for review: Nutrient-dependent/pheromone-controlled adaptive evolution: a model.
October 18, 2013
This is the first I've seen that this argument about all early hominids belonging to a single species is based on the evidence about one group of hominids in one gorge in southwestern Asia. I would expect all of the hominids found in one place, even from a wide range of time, to not have more morphological variation from each other than do modern humans or orangutangs.
The article actually doesn't show us what sort of morphological dissimilarity was found; for instance, early hominids had tremendous sexual dimorphicity. Males were twice as big as females, and that was probably for starters.
I don't know why someone would be telling us what all early hominids belonged to based on evidence from one gorge.
The notion that all early hominids were a single species is nonsense. There was too much variation, too much change in features, too much variety living at one time, and, I believe, even side lines that didn't go anywhere.
In short, besides being based on way too limited evidence, this article is a semantic debate. It is the same sort of debate as whether birds are really dinosaurs or merely evolved from them.
Are you sure the author of this study isn't English? Because this kind of very silly debate goes on there all of the time. It's a favorite sport among the British upper classes.
October 18, 2013
Absolutely stunning discovery ! Am sure there is more there than meets the eye. Waiting to hear more about the environment in which this discovery was made. Any other artifacts preserved on this site ?.....any signs/fossils of food, forage, tools ?
October 18, 2013
Re: It is the same sort of debate as whether birds are really dinosaurs or merely evolved from them.
To a degree this is true. If any species evolved from another, it could only be due to conserved molecular mechanisms that are nutrient-dependent and pheromone-controlled in species from microbes to man. Across this evolutionary continuum of epigenetic cause and effect, there is experimental evidence only for nutrient-dependent ecological niche construction, and that's what is addressed in the article about Skull 5.
Thus, if you are willing to propose an alternative means to evolution that does not involve ecological niche construction, we could enter debate about what you might like to call evidence that all early hominids were not conspecifics with variable nutrient-dependent morphogenic traits, such as those of Skull 5 Instead, you label their ecological perspective on Skull 5 "nonsense" despite the variations we see in many other species, all of which are nutrient-dependent and controlled by the metabolism of nutrients to species-specific pheromones, which control reproduction.
October 21, 2013
Perhaps, especially the sexual dimorphism, but never forget the range of traits in living species. Never forget that speciation is simply when 2nd generation offspring cannot reproduce; there is too much missing datan but it is an exciting hypothesis. Humans have very little genetic diversity, but we have an interesting array of bone structures(much of it epigenetic, but epigenetics would have some role in early hominid variation as well). There are a lot of possibilities.
Better yet, look at domesticated dogs as a species. I look forward to more data/samples being found.