The coelacanth, a fish thought to have gone extinct 60+ million years ago and the Wollemi Pine, a species of plant that apparently went the way of the dinosaur about 90 million years ago, don't appear to have evolved any. As both lifeforms seem to appear as they do in the fossil record, the question is: why didn't they evolve? I don't trust Wiki but it claims minor evolutionary changes in the fish have occured. Whether this is true or not I can't tell you. On the other hand, I can't seem to find an article that claims the tree has evolved at all. I would certainly like to know if evolutionary changes are evident when comparing the live species samples with the fossil records. I realize that it may be too difficult to examine some features of either lifeform in a fossilized rock. No matter, is it a hard fast rule that all lifeforms evolve? If the fish & the tree did not, is it because they are superadaptive, or didn't need to adapt? Of the countless billions of creatures that have existed since life started here, I do believe it possible that not every one would have continued to evolve. That said, it does seem quite remarkable that two species from prehistory happen to be around. Call it luck or coincidence. I realize such lifeforms are fodder for the creationists but I have to believe the fish & the tree have undergone some minor changes at minimum. Can someone with more knowledge on the subject enlighten me somewhat?
They have probably developed resistance to some diseases through annihilation of less resistant specimens. They may grow to different sizes now depending on the availability of foods. They probably haven't changed significantly because there is little pressure to do so. They have their niche, nothing is threatening that, they are successful at breeding, so carry on. There will be minor changes through less than perfect replication, and these can be tracked in the case of the coelacanth through mitochondrial DNA, and I guess through RNA for the pine.
Yes, of course they have evolved. The modern coelacanth does resemble the fossils in appearance, but things like internal organs and behavior have certainly changed. I saw a documentary on this fish, and this aspect was mentioned, I don't remember all the details. It is thought the coelacanth might have survived by changing it's feeding habits. Nothing just stops evolving, there is no mechanism that completely prevents genetic variations from occurring.
There is a theory that retroviral agents play a signficant role in evolution by injecting genetic material into the host...makes a lot of sense to me. If such is the case, then perhaps this fish has been slow to evolve because of an immune system that is resisstent to retrovirus.
Or maybe it did split off into other species, the original happening to find a stable environmental niche.
Some things change very slowly, particularly if they are already well adapted. Redwood trees existed very much like the ones extant today during the dinosaur era. The deciduous "Dawn Redwood", aka Metasequoia glyptostroboides, had been known only from fossils from the dinosaur era for many decades, when several live species were 'discovered' growing in China in the 1940s. Of course, we can only tell that the gross morphology looks almost exactly the same. Internal genetic differences, from random genetic drift and evolutionary drift, that don't give rise to gross morphological differences, would not be detectable from the fossil record. Redwood trees appear to be remarkably well-adapted to their environment and have little environmental pressure differences on them during the age of mammals compared to the age of reptiles of many millions of years ago.
That's the problem with evolution and long-extinct species: change in allele freqs isn't evident from fossilized remains. Of course, they did get some DNA out of that frigging Tyrannosaur femur (bastards) so that'll probably change too, and then everything will be boring and categorized. My cousin was a paleontologist. Why can't I be a paleontologist? Sucks.
I read the Wollemi pine book a few years ago, and seem to remember something about the remaining population basically being clones- each specimen having identical DNA with no variation as with a normal population. This may be the reason why there was no further evolution, as the process requires genetic variation from which to select? Obviously the species has adapted superbly to fit the niche, which is quite a unique place. As an aside, there is an intense horticultural program to grow them, with one of the nurseries only 20kms from me, and flood the market to protect the originals (and also ensure their survival if that niche is compromised). I've seen several 2-3metre specimens behind bars in public parks, and I had a small one given to me. What millions of years in an extreme microclimate couldn't kill, I managed!Please Register or Log in to view the hidden image! Cheers, Bric
Yeah. Evolution is defined as changes in allele frequency, and it's hard to imagine allele frequencies remaining static for 60 million years, innit? Given their small populations, I suspect that drift has played an important roll in their evolution.
