or adapiforms. They also lack the skull specializations 

 of anthropoids. Their teeth also come in a wide va- 

 riety of forms, some of which, in most details, re- 

 semble the teeth of amphipithecids. But the greatest 

 similarities lie in the skeleton. In fact, if you carried 

 an upper arm bone of Pondaungia to Wyoming and 

 laid it on a hill in the badlands, the next paleontolo- 

 gist to come along would readily identify it as an 

 adapoid. Pondaungia resembles the known Wyoming 

 adapoids so closely that no one would be surprised 

 to find it there [see illustration on opposite page}. 



Most of the adapoids became extinct before 40 

 million years ago, but some from coastal California 

 and coastal Texas survived longer. The latter, like the 

 amphipithecids, some of which lived as late as 34 

 million years ago, probably represented relict popu- 

 lations that survived in isolated tropical belts near 

 coastal areas. There the cool and dry climate typical 

 of the continental interiors had yet to take hold. 



The amphipithecids were the first Eocene pri- 

 mates to be recognized from Asia. For many 

 years, in fact, their fossil remains constituted the on- 

 ly evidence in support of a possible Asian ancestry 

 for anthropoids. Some scholars still advocate that 

 view. In recent years, however, a new group of pri- 

 mates known as the eosimiids has replaced the am- 

 phipithecids as the leading Asian candidate for the 

 title "earliest anthropoid." The eosimiids were small 

 animals that have some dental features in common 

 with early Fayum anthropoids. Paleontologists who 

 champion them as anthropoid ancestors suggest that 

 the group, like the amphipithecids, arose in Asia and 

 subsequently dispersed into Africa. The difference is 

 that the eosimiids would have had to begin migrat- 

 ing out of Asia more than 60 million years ago. 



Such an early dispersal, however, is hard to square 

 with geographic reality. A wide body of water 

 known as the Tethys Sea separated Africa from Asia 

 60 million years ago. An arm of that sea, known as 

 the Obik Sea, divided Asia from Europe. The pre- 

 vailing ocean currents would have prevented most 

 animals from rafting from Asia to Africa or from Asia 

 to Europe and then on to Africa. There is evidence 

 of limited migration between Africa and Europe as 

 early as 60 million years ago, but no sign of an 

 African-Asian interchange. Not until much later, 

 about 33 million years ago, is there evidence of even 

 limited migration between Africa and Asia. 



There are more problems for the hypothesis that 

 eosimiids were the first anthropoids. Like amphi- 

 pithecids, eosimiids are known only from highly 

 fragmentary specimens, and many features of their 

 teeth look decidedly nonanthropoid. Moreover, like 

 the fossils of the amphipithecids, the known fossils 



Notharctus venticolus, an adapoid shown here in an artist's reconstruction, 

 inhabited what is now Wyoming about 50 million years ago. Although the 

 adapoids left no living descendants, they remain part of the broad picture of 

 primate origins. 



of eosimiids are too young. The earliest known 

 eosimiid fossils date from 47 million years ago, 

 whereas African anthropoid fossils from Algeria go 

 back at least 50 million years. (A 60-million-year- 

 old Moroccan fossil may also be an anthropoid, but 

 that conclusion is in dispute.) At best, the eosimi- 

 ids may represent an early, Asian anthropoid lineage 

 that turned out to be an evolutionary dead end. 



In short, the search for the earliest anthropoid an- 

 cestor must go on. Whether that elusive creature 

 lived in Asia or Africa, or even Europe or North 

 America, is still a puzzle that future paleontologists 

 will have to solve. □ 



March 2006 NATUIlAl HISTORY 



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