Island Evolution and What's More
by Alexandra van der Geer, (NBC Naturalis & NKUOA, Greece)
Monday, July 7, 2014
Role of predators overrated
Tuesday, December 3, 2013
A new invasion, or what happens next
Tuesday, June 5, 2012
Contextual evolution on islands
Tuesday, September 14, 2010
Evolution of Island Mammals
If you are interested in the evolution of insular mammals, from the Eocene walking sirenian (Pezosiren portelli) of Jamaica to the recently extinct Falkland Wolf or Fox (Dusicyon australis) of the Falkland Islands and the still living island fox (Urocyon littoralis) of the Californian Channel Islands, this book is a must. It offers a complete overview of all fossil and most recently extinct mammals that once upon a time lived on islands somewhere on our planet. They were fully adapted to their environment, and often evolved bizarre features, like elongated, club-like antlers with hardly any tines (the deer Candiacervus of Crete), ever-growing front teeth (the bovid Myotragus of Majorca), enormous size (the cavia-like Amblyrhiza of the West Indies) or pygmy size (the hominid Homo floresiensis of Flores).
Unfortunately, the majority of them went extinct, often after spectacular long periods of gradual evolution in situ, when mainland colonisers discovered the islands and their fauna. Today, just a few islanders survived, in comparison with the number of islanders of the remote past. Their special features are unique, but in most cases less spectacular than seen in the fossil record, when elephants could shrink till a mere one or two percent of the body mass of their ancestral size (as in the case of Elephas falconeri).
To have an idea of how extreme evolution can be, you have to see the fossil islanders!
Wednesday, November 4, 2009
Dental eruption sequence of a fossil 'baboon' (Paradolichopithecus arvernensis)
We further found that the eruption sequence of the permanent mandibular dentition of this male is {m1 i1–2 m2} p4, p3, c, m3. The order of the already fully erupted elements (between curly brackets) is based on data from the living baboons, mandrills, macaques and geladas. The p4 p3 sequence as seen in our Paradolichopithecus occurs at high frequency is other papionins as well: Macaca nemestrina, M. mulatta, Mandrillus sphinx, Papio cynocephalus, but not in Papio anubis, Macaca fuscata and M. fascicularis. Theearlier root formation of p4 seems thus not to be related with body size or phylogeny. There is a considerable delay in the canine development relative to the premolars, as in other papioninmales; the m3 is delayed in formation relative to the premolars and the canine. In total, the dental eruption sequence of Paradolichopithecus is very similar to that of the living papionins.
Read more in Van der Geer, A.A.E., Dermitzakis, M. 2008. Dental eruption sequence in the Pliocene Papionini Paradolichopithecus arvernensis (Mammalia: Primates) from Greece. Journal of Vertebrate Paleontology 28 (4): 1238-1244. (Ask a pfd, geeraae@geol.uoa.gr)
Wednesday, August 6, 2008
'Hobbit' skull found in Indonesia is not human indeed
Since its first description in 2004, Homo floresiensis, or the Hobbit of Flores, has been attributed to a species of its own, a descendant of Homo erectus, Homo ergaster or another early hominid, such as Australopithecus. Non-believers however hold the new species for a pathological form of modern humans, Homo sapiens, or just a dwarf human like the Neolithic inhabitants of the very same island. Karen Baab and colleagues applied landmarks on the skull, and concluded Homo floresiensis is a species on its own, and related to hominins of 1.5 million years ago. We did the same, half a year earlier, and reached similar conclusion but dare to put one step further. We applied geometric morphometric analysis to the type skull of Homo floresiensis (LB1) and compared it with skulls of normal Homo sapiens, insular Homo sapiens (Minatogawa Man and Neolithic skulls from Flores), pathological Homo sapiens (microcephalics), Asian Homo erectus (Sangiran 17), African Homo habilis (KNM ER 1813), and Australopithecus africanus (Sts 5). Our analysis includes specimens that were highlighted by other authors to prove their conclusions. The geometric morphometric analysis separates the 'hobbit' from all modern humans, thus including both the pathological and the insular forms. It is further impossible to separate the 'hobbit' skull from Homo erectus. The very early hominin Australopithecus falls separately from all skulls.
Visual inspection of the skulls learned that the cranial shape of Homo floresiensis is most close to that of Homo erectus and not to that of any modern human. Apart from cranial shape, some features of Homo floresiensis are not unique but are shared with other insular taxa, such as the relatively large teeth (shared with Early Neolithic humans of Sardinia), and changed limb proportions (shared with Minatogawa Man).
We thus conclude that Homo floresiensis is a direct descendant of Asian Homo erectus and has no relation neither to primitive australopithecines nor to modern Neolithic pygmy people of Flores.
By G.A. LYRAS, M.D. DERMITZAKIS, A.A.E. Van der GEER, S.B. Van der GEER, J. De VOS. 2008. The origin of Homo floresiensis and its relation to evolutionary processes under isolation.© 2008 The Anthropological Society of Nippon
For free pdf, click here http://users.uoa.gr/~glyras/projects/Homo-floresiensis.pdf
Or go to the publisher http://www.jstage.jst.go.jp/browse/ase
The effect of insularity on the five-horned deer Hoplitomeryx (Late Miocene, Italy)
Read more in VAN DER GEER A.A.E. (2008). The effect of insularity on the Eastern Mediterranean early cervoid Hoplitomeryx: the study of the forelimb. Quaternary International 182, 1: 145-159. See http://dx.doi.org/10.1016/j.quaint.2007.09.021 or ask me a pdf (geeraae@geol.uoa.gr).
For more general information of this enigmatic Late Miocene 'deer', see my Wikipedia page at http://en.wikipedia.org/wiki/Hoplitomeryx