Friday, 30 October 2015

Transitional Human Ancestor From Spain

Reconstruction of the skull and representation of Pliobates cataloniae.

Miocene small-bodied ape from Eurasia sheds light on hominoid evolution

I said the other day that this was shaping up to be another bad week for creationists (are there ever any good ones?). Now scientists have only gone and found another of those 'non-existent transitional fossils'.

This one is from the our branch of the evolutionary tree at a point soon after the divergence of primates into the Old World or catarrhine monkeys and the anthropoid apes and close to the point where the anthropoid branch diverged again into the gibbons or hylobatids and the hominoids (great apes, including humans). It suggests that the last common ancestor of ours and gibbons was more gibbon-like than has generally been assumed.

It has been described by a team of palaeobiologists from Institut Català de Paleontologia, Catalonia, Spain. It was found in Miocene deposits in Spain and dates from 11.6 million years ago.

Miocene small-bodied anthropoid primates from Africa and Eurasia are generally considered to precede the divergence between the two groups of extant catarrhines — hominoids (apes and humans) and Old World monkeys — and are thus viewed as more primitive than the stem ape Proconsul. Here we describe Pliobates cataloniae gen. et sp. nov., a small-bodied (4 to 5 kilograms) primate from the Iberian Miocene (11.6 million years ago) that displays a mosaic of primitive characteristics coupled with multiple cranial and postcranial shared derived features of extant hominoids. Our cladistic analyses show that Pliobates is a stem hominoid that is more derived than previously described small catarrhines and Proconsul. This forces us to reevaluate the role played by small-bodied catarrhines in ape evolution and provides key insight into the last common ancestor of hylobatids (gibbons) and hominids (great apes and humans).*

Miocene small-bodied ape from Eurasia sheds light on hominoid evolution
David M. Alba, Sergio Almécija, Daniel DeMiguel, Josep Fortuny, Miriam Pérez de los Ríos, Marta Pina, Josep M. Robles, Salvador Moyà-Solà
Science 30 October 2015 Vol.350 no.6260. DOI: 10.1126/science.aab2625

*Copyright © 2015, American Association for the Advancement of Science. Reprinted with permission (licence #3738820421699)

The fossil fragments, which provide enough material to reconstruct the cranium, the wrist and the elbow show a mosaic of features from both the stem catarrhine monkeys and the more advanced hominoids, in other words, this specimen shows evidence of transition between the small-bodies monkey ancestors and the early anthropoids apes. The differences are due to the basic modes of locomotion along tree branches. The monkeys generally walk above the branch on all four limbs whereas the anthropoids generally brachiate, i.e. they hang below the branch and swing along. This change in locomotion needed changes to the wrist and elbow joints.

The scientific significance of this is not, of course, the fact that this is a transitional form - that issue was long ago dispensed with by serious evolutionary biologists if it ever was an issue - but the fact that might require us to reassess when we thought we knew. It has generally been assumed that the anthropoids evolved out of large-bodied monkeys and that the gibbons represent a subsequent dwarfing of the basic body plan. Now it seems the early stem anthropoids may have been closer to the small-bodied Old World Monkeys.

For creationists, the significance of this find is that it's just one more thing to either ignore altogether or to lie about.

Yep! This looks like being yet another bed week for creationists.

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