Expert: John Shea - 12/28/2009

Question
QUESTION: Hi John,my friends,who like to believe in alien intervention etc,are always quoting to me 'the missing link'. Has the tracing of human evolution been more problematic than that of animals? Has there been a missing link for humans,and if so has that been found now? Are we confident that we can trace human evolution as well as some animal evolution? As a believer in Darwinism and someone who likes to win an argument!! i would appreciate your thoughts. Thankyou for your time   Regards Richard.

ANSWER: There is really no such thing as "a" missing link.  The fossil record is discontinuous, so in the gaps between any two fossils is filled with many "missing links".
The most common usage of the term refers to the last common ancestor of humans and living apes.  Genetic studies suggest this creature lived around 6 million years
ago.  The fossil record for this period is kind of sparse, probably because it followed a period of intense mountain-building and accelerated erosion. But,
paleontologists are finding a lot more evidence from this period.  We will probably never identify a specific fossil or a specific fossil species as "the" missing link.  Rather
there will be a bunch of morphologically-similar competitors for this title.
Back in September, I heard Peter Kjaergaard read a paper about the "missing link" at the CALPE 2009 confernce in Gibraltar.  It was very interesting.  He is at Cambride University in the UK. You might have a look to see what he has written on published
about this issue.
If it helps, you might point out to your "alien intervention" friends that the weakest evidence for human evolution is still immeasurably stronger than the strongest "evidence" for extraterrestrial visits to Earth.
Cheers,
John Shea

---------- FOLLOW-UP ----------

QUESTION: Thankyou John for your reply. Quite informative,but would just like a bit more clarification on one point i made. Is there a fundemental difference studying human evolution to animal evoltion? Is it harder to do? Do 'we' spend less time investigating human evolution compared to animal evolution (given that there are more animals!) There seems to be a laymans view that we have animal evolution down pat and human evolution is vague,leading to weird views of our evolution. The gaps you mention in fossil records for humans are surely the same in some animal fossil records. Once again thankyou very much  Regards  Richard

Answer
Dear Richard
Sorry, I neglected to answer the other part of your question.  There is, in principle, no difference between the methods paleontologists
investigate human evolution and the way they investigage the evolution of other animals.  They use comparative anatomy, genetics, and paleontology to'
develop testable hypotheses then set out to refute them.  The main difference is that most people are more interested
in human origins than they are in the origins of other species.  So, fossils that have a credible claim to primate, hominin, or human ancestry get a lot more
attention and publicity than fossils ancestral to, say, horses, muskrats, or kangaroos.  Want proof?  When was the last time Science had a special issue devoted
to a fossil ancestor of one of these taxa vs. say the recent issue devoted to Ardipithecus ramidus?
One other difference is that human evolution tends to attract "lunatic fringe" theories more so than evolutionary research on other subjects.  All kinds of crazy stuff
gets written about human evolution for which there are few parallels in the literature of other animal lineages.  Case in point, the alien intervention stuff you mentioned
in your first message.
Cheers
John Shea