Living fossils
December 10th 2008 05:45
Wired magazine has listed 12 "living fossils" for your edification. A living fossil is a species that appears to have changed very little over geological time right up to the present day. The iconic living fossil is the Coelacanth, a sarcopterygian that was discovered alive in 1938 off the coast of South Africa (and has been found subsequently in other places). The term living fossil is actually somewhat misleading. It implies that these species haven't changed at all, but since we have only fossil data, we can't tell to what extent these lineages have changed at the molecular level, or whether non-fossilised parts of their morphology have changed. Indeed, these may well have changed. Another thing to keep in mind is that these species, while they may bear a striking resemblance to their kin in the fossil record, are not necessarily any less efficient than other species that show more derived character states. Clearly, if they have survived to the present day, they must have had what it took to get here, either because of the aforementioned non-fossilised aspects of their make-up, or because their ancestral biological design has sufficed in the environments in which they live. It is possible that these designs are in fact so efficient that stablilising selection has kept them there. Finally, some people are apt to see these species as "proof" that evolution is a fraud, because, to their minds, evolutionary theory necessitates that all species must evolve; finding species that seem to have stayed the same for a long time therefore means that evolution cannot account for them. This is wrong on two counts. Firstly, evolutionary theory doesn't necessitate that a species must evolve. There are factors that could see a species remaining the same indefinitely, for the reasons I stated above, or perhaps because of some homeostasis that prevails in the species' genetic or developmental architecture. Secondly, evolution is clearly visible in the fossil record, so finding evidence of lineages that have undergone little or no evolution simply presents us with another problem: why haven't these lineages evolved?
Continue reading here.
Continue reading here.
| 51 |
| Vote |
