Monday, May 22, 2017

Graecopithecus Casts Doubt on "Out of Africa" Story of Human Origins

As reported in PLOS | One today, a 7.2 million year old fossil named Graecopithecus, from late Miocene Europe, suggests that the human line may have originated in the Eastern Mediterranean (i.e. Europe), not Africa.  
"In this study, we propose based on root morphology a new possible candidate for the hominin clade, Graecopithecus freybergi from Europe. " [...]
"In contrast to the Ponginae, Graecopithecus shares derived characters with African apes (ventrally shallow roots, buccolingually broad molar roots; [32, 75]). Therefore, we consider four principle alternative interpretations of its phylogenetic position: Graecopithecus is a stem-hominine (last common ancestor of African apes and Homo), a gorillin, a panin, or a hominin." [...]
"Accordingly, the most parsimonious interpretation of the phylogenetic position of Graecopithecus is that it is a hominin, although we acknowledge that the known sample of fossil hominin root configurations is too small for definitive conclusions."[...]
"Taken at face value, the derived characters of Graecopithecus (p4 root morphology and possibly canine root length) may indicate the presence of a hominin in the Balkans at 7.2 Ma." [...]
"Therefore, we submit that the dental root attributes of Graecopithecus suggest hominin affinities, such that its hominin status cannot be excluded. If this status is confirmed by additional fossil evidence, Graecopithecus would be the oldest known hominin and the oldest known crown hominine, as the evidence for the gorillin status of Chororapithecus is much weaker than the hominin status of Graecopithecus [8]. More fossils are needed but at this point it seems likely that the Eastern Mediterranean needs to be considered as just as likely a place of hominine diversification and hominin origins as tropical Africa."
Phys.org provides more information on Graecopithecus: apparently the species inhabited a savannah habitat and remains were found with large grass-feeding herbivores.
"The phytolith record provides evidence of severe droughts, and the charcoal analysis indicates recurring vegetation fires," said Böhme. "In summary, we reconstruct a savannah, which fits with the giraffes, gazelles, antelopes, and rhinoceroses that were found together with Graecopithecus," Spassov added.
"The incipient formation of a desert in North Africa more than seven million years ago and the spread of savannahs in Southern Europe may have played a central role in the splitting of the human and chimpanzee lineages," said Böhme. She calls this hypothesis the North Side Story, recalling the thesis of Yves Coppens, known as East Side Story.
More information: Potential hominin affinities of Graecopithecus from the Late Miocene of Europe, PLOS ONE (2017). journals.plos.org/plosone/article?id=10.1371/journal.pone.0177127
Messinian age and savannah environment of the possible hominin Graecopithecus from Europe, PLOS ONE (2017). journals.plos.org/plosone/article?id=10.1371/journal.pone.0177347


Read more at: https://phys.org/news/2017-05-scientists-million-year-old-pre-human-balkans.html#jCp
 The full text is "Messinian age and savannah environment of the possible hominin Graecopithecus from Europe" at PLOS | One.

This might support my suggestion that humans are descended not from a chimpanzee-like frugivore, but a savannah-dwelling largely or heavily insectivorous (i.e. carnivorous) ancestor .  As I wrote there:

....before there existed some putative pre-human (i.e. non-human) ancestors who ate plant-based diets, the ancestors of the primate line were insectivores, i.e. carnivores who specialized in eating insects.  From anthro.palomar.edu:
"Transitional primate-like creatures were evolving by the end of the Mesozoic Era (ca. 65.5 million years ago)....The few placental mammals that existed at that time mainly consisted of the insectivore ancestors of primates."
These carnivorous ancestors of primates continued until about 55 million years ago when some creatures resembling modern prosimians emerged.  But anthro.palomar.edu notes:
"Among the numerous Miocene primate species were the ancestors of all modern apes and humans.  By 14 million years ago, the group of apes that included our ancestors was apparently in the process of adapting to life on the edges of the expanding savannas in Southern Europe." 
[Graecopithecus was found in Southern Europe.]

The human line descends from those primates that specialized in living on the savannas, not those – like the ancestors of chimps – that specialized in the arboreal habitats.  On savannas, the predominant form of plant-life is grass, while fruits are relatively scarce, especially during Ice Ages.  Thus, an animal can thrive on a savanna only if it eats grass, or animals that eat grass.  Humans are obviously not grass-eaters – we don't have the multi-compartment guts adapted to fiber fermentation that is typical of grass-eating animals.  But an insectivore can find plenty of grass-eating insects, such as grasshoppers, caterpillars, moth larvae, grubs, crickets, and billbug larvae.  It can also find small grass-eating molluscs like snails.

The nutritional profile of insects is quite similar to wild game:

Insects are wild game.  Therefore an insectivore is already a predator adapted to eating wild game.  Insectivores have simple, carnivore-type guts.   An insectivorous species would have to evolve new behaviors or gut features – hindgut fermentation vats – to become predominantly frugivorous and deal with the fiber abundant in plants, as has occurred in the great apes but not in humans. The great apes have enormous guts adapted to fermenting fiber to convert it into saturated fats, mostly butyrate; healthy humans do not:

We have strong evidence that early Pleistocene humans – definite members of our genus – were ambush predators 2 million years ago.   We know that all definitely human ancestors –  from Homo habilis 2 mya to present – were hunters and meat-eaters.  Dunn could justify his claim only by referring to the putative habits of ancient species who were not human and are only suspected human ancestors (e.g. Australpiths), while ignoring the heavy meat-eating habits of those species that we know were human.  Is that scientifically honest?

The truth is all known human ancestors of modern humans, i.e. Homo habilis, Homo erectus, Neanderthals, and Denisovans were predators, not vegetarians.  Only non-human species that might have been part of the human lineage,  such as Austalopiths, were largely plant-eaters.  The hypothesis that human ancestors were nearly all vegetarians can't explain what we know about human evolution, and does not align with what we know about the Earth's climate, flora and fauna changes during the period of time when the human lineage evolved and moved out of Africa. 

An insectivore is a hunter, a predator.  Humans have been deliberate predators for at least 2 million years.  Which is the most likely evolutionary scenario: 


THEORY 1:

While the savannas are expanding and forests shrinking during the millions of predominantly Ice Age years, natural selection acts on an insectivorous savanna species to favor those that prefer to eat fruits and vegetables that don't exist on the savanna and are disappearing due to the cold and dry climate, ultimately converting that insectivore with a simple carnivore-type gut into a frugivorous, hindgut fermenter arboreal species; then natural selection changes course completely, starts favoring the savanna-dwelling meat-eaters among those fruit-eaters, progressively selects against the hindgut fermenters and eventually changes the members of this lineage back into a savanna-dwelling apex predator species with a relatively simple, reduced volume carnivore-type gut with gastric acidity greater than most carnivores and comparable to scavenger species (the human line starting at least 2 mya with Homo habilis).

Source:  Voegtlin, The Stone Age Diet, p. 44
Source:  Voegtlin, The Stone Age Diet, p. 45
THEORY 2:

While the savannas are expanding and forests shrinking (starting towards the end of the Miocene, up to ~ 6 mya), natural selection favors the reproduction of those members of an  insectivorous savanna species who capitalize on the increasing abundance of grass-eating insects, then favors those who can capture and eat the even more energy-dense grass-eating mammals (various rodents such as rabbits and gerbils), then among those favors the individuals who are able to capture larger and larger, more and more energy-dense, fat-rich game, ultimately transforming the originally puny predatory primate (the insectivore) into a mega-primate, the most predatory ape of all, the human, who hunted elephants for a living?

It seems to me that the second scenario is far more likely to be what happened.  In fact, due to the biological leaps and outright reversals (in dentition and intestinal form and function) required, I would venture that the probability of the first scenario is near zero.  If chimps and humans have a common ancestor, that ancestor was likely primarily an insectivore (chimps still are somewhat insectivorous).  The chimp line likely represents the descendants of that last common ancestor (LCA) who chose to specialize in an arboreal habitat.  The descendants of the LCA who specialized in a savanna habitat retained their dominant predatory way of life, and this line slowly graduated from insects and worms to snakes, amphibians and other small animals, then to larger and larger savanna animals until finally the highly carnivorous human emerged by 2 mya.

 

More information: Potential hominin affinities of Graecopithecus from the Late Miocene of Europe, PLOS ONE (2017). journals.plos.org/plosone/article?id=10.1371/journal.pone.0177127
Messinian age and savannah environment of the possible hominin Graecopithecus from Europe, PLOS ONE (2017). journals.plos.org/plosone/article?id=10.1371/journal.pone.0177347


Read more at: https://phys.org/news/2017-05-scientists-million-year-old-pre-human-balkans.html#j

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