CHICAGO - New research that accounts for gaps in the fossil record challenges traditional methods of interpreting fossils and constructing evolutionary trees. Applying a new statistical approach to primates demonstrates that this group-from which humans developed-originated 85 million years ago (Mya) rather than 65 Mya, as is widely accepted.

This revision has implications throughout the evolutionary tree of primates, including the time of origin of the human lineage. Key findings from the new approach to interpreting the fossil record include:

• Primates originated while dinosaurs still roamed the earth. This challenges the
  widely accepted theory that primates could not establish a foothold until the end of the Cretaceous (65 Mya) when an asteroid cleared the way by hitting the earth and wiping out dinosaurs.

• If times of divergence within the primate tree are revised accordingly, it is likely that the divergence of humans from chimps occurred
  about 8 Mya rather than 5 Mya.

• An earlier origin for primates makes it very likely that continental drift played an important part in initial geographical subdivisions within primates.

• The new approach supports previously disputed findings from several molecular evolutionary trees calibrated with fossil dates from better-known parts of the mammalian tree. Calibrations outside the primates include mammal-like reptiles, horses and cetaceans (whales, dolphins and porpoises), where the fossil record is much more complete.

• Using the fossil record to date the origin of any group for which the fossil record is sparse (including certain other mammals, such as bats) is unreliable.

"Current interpretations of primate and human evolution are flawed because paleontologists have relied too heavily on direct interpretation of the known fossil record," says Robert D. Martin, PhD, vice president of academic affairs at The Field Museum a
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Contact: Greg Borzo
gborzo@fieldmuseum.org
312-665-7106
Field Museum
17-Apr-2002