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Darwin's "Extreme" Imperfection?


"Darwin used the words "extreme imperfection" to refer not to any personal character flaw but to the gappy nature of the fossil record (Darwin 1859). The vast majority of organisms that have lived on Earth never fossilized. Jellyfish and worms? Too squishy to fossilize very often. Butterflies? Too delicate, for the most part. Anything that lived on mountain slopes or in fast-moving rivers? Unlikely to be covered by sediment and preserved. Darwin saw such haphazard preservation as a serious problem for the theory of evolution. After all, he was proposing that different modern species share common ancestors--that organisms as different as lobsters and butterflies have the same great-great-great-great...great-grandparent species. Direct fossil evidence of all the intermediate forms connecting an ancestor to its modern descendents would have provided undeniable evidence in favor of his theory. In Darwin's view, however, the fossil record provided no such support. Much of On the Origin of Species is taken up with marshaling other forms of evidence to support his ideas about common ancestry and natural selection.

In an article included in this issue (Charles Darwin and Human Evolution), Ian Tattersall (2009) proposes that Darwin's disparaging view of the fossil record, along with other factors, might help explain why Darwin did not write more about human evolution. Tattersall notes that some fossils shedding light on human evolution had been discovered at the time of Darwin's writing but that the area was tainted by fraud and controversy. Darwin may have viewed our own fossil history as just another gap in the fossil record--one which might never be filled by hard evidence. Though he clearly accepted the idea that humans evolved from ape ancestors, Darwin may have curtailed his discussion of this transition partly because of the evidence he wanted, but did not have: fossils of so-called missing links. Here, we will dig into the concept of a missing link to see whether this is the problem for evolutionary theory that Darwin imagined and to find out
what we have learned about this sort of evidence since Darwin published his ideas in 1859."