Given all the species that exist and have existed, there should be
billions of transitional fossils in the fossil record; we should have
found tens of thousands at least.
- Some important factors prevent the formation of fossils from being
- Fossilization itself is not a particularly common event. It
requires conditions that preserve the fossil before it becomes
scavenged or decayed. Such conditions are common only in a very
few habitats, such as river deltas, peat bogs, and tar pits.
Organisms that do not live in or near these habitats will be
preserved only rarely.
- Many types of animals are fragile and do not preserve well.
- Many species have small ranges. Their chance of fossilization will
be proportionally small.
- The evolution of new species probably is fairly rapid in geological
terms, so the transitions between species will be uncommon.
Passenger pigeons, once numbered in the billions, went extinct less
than 200 years ago. How many passenger pigeon fossils can you find?
If they are hard to find, why should we expect to find fossils that are
likely from smaller populations and have been subject to millions of
years of potential erosion?
- Other processes destroy fossils. Erosion (and/or lack of deposition in
the first place) often destroys hundreds of millions of years or more
of the geological record, so the geological record at any place usually
has long gaps. Fossils can also be destroyed by heat or pressure when
buried deep underground.
- As rare as fossils are, fossil discovery is still rarer. For the most
part, we find only fossils that have been exposed by erosion, and only
if the exposure is recent enough that the fossils themselves do not
As climates change, species will move, so we cannot expect a transition
to occur all at one spot. Fossils often must be collected from all
over a continent to find the transitions.
Only Europe and North America have been well explored for fossils
because that is where most of the paleontologists lived. Furthermore,
regional politics interfere with collecting fossils. Some fabulous
fossils have been found in China only recently because before then the
politics prevented most paleontology there.
- The shortage is not just in fossils but in paleontologists and
taxonomists. Preparing and analyzing the material for just one lineage
can take a decade of work. There are likely hundreds of transitional
fossils sitting in museum drawers, unknown because nobody knowledgeable
has examined them.
- Description of fossils is often limited to professional literature and
does not get popularized. This is especially true of marine
microfossils, which have the best record.
- If fossilization were so prevalent and young-earth creationism were
true, we should find indications in the fossil record of animals
migrating from the Ark to other continents.
Hunt, Kathleen. 1997. Transitional vertebrate fossils FAQ, part 1A.
Kidwell, S. M. and S. M. Holland. 2002. The quality of the fossil record:
Implications for evolutionary analyses. Annual Review of Ecology and
Systematics 33: 561-588. (technical)
created 2003-7-11, modified 2004-1-29