|Goblin Shark. wiki|
Anyways, today I want to write about the concept and use of the term "living fossils" and how- useful to some extent- it is one of the more abused and misapplied concept in biological discourse. You may recall that I did a piece a while ago on crocodiles and how the entrenched concept of crocs as static unchanging river lurkers is simply not true. And this pop science mantra of "living fossil" is often applied to cycads, sharks, ferns, marsupials, and conifers among others. But the application of this term can be misleading, for instance all extant cycads show evidence of Tertiary origin and may actually be diversifying presently. The main problem I find is that the term 'living fossil" implies a sort of biological anachronimism, a creature out of place and time for which evolution has abated all together. And this is the big danger I find in throwing around the term "living fossil" because it suggests that evolution will stop and start as if under some internal control or suggests a type of evolutionary senility. And this is why I prefer to speak of living fossils as relict species and not as "living fossils". The term "living fossil" also suggests a lack of adaptive vitality- that the species is not well adapted to its environment. But, in truth what often occurs is that environments diminish in size and, through no fault of its own, the critter adapted to this environment diminishes in number with it. From our perspective we see a creature/family limited in diversity and number due not to any intrinsic maladaptive qualities but simply a loss of the correct conditions it thrives in. And sometimes, due to anthropogenic intervention, these relict species can be redistributed throughout the world- such as in the case of Gingko trees, Dawn redwoods and Wollemii pine.
And this concept of "living fossils" and the associated misconceptions that commence from its use also contribute sometimes to a view of whole ecosystems/communities sharing characters consistent with a veritable "lost world". And one of the more consistently put forth habitats that purportedly displays such a character is the abyssal realm of the deep ocean. And at first glance this cold, isolated, dark, pressurized realm would seem to be the ideal place to expect some long lost tribe of relict critters to persist. Indeed once a group adapted to such a realm you would expect them to enjoy a particularly long tenure there would you not? And for this reason the famed deep sea vent communities have been suggested as not only representing some of the oldest communities of life on this planet, but have also been suggested to represent the start of life itself on this planet. Except they are not. And the reason that deep sea vent communities and most likely all deep abyssal life in general occasionally goes through a major evolutionary reset is summed up in two words: anoxic events.
|(c) Emory Kristof. Nat Geo|
So, in summary, the term "living fossil" is, at best I would argue, a loaded term. I prefer the term "relict species" but even here we run into trouble because, barring concrete evidence of cryptic hominids, we ourselves are a relict species. After all we are the last in line of a formerly much more diverse radiation of bipedal apes?
Novel Tools for an Old Lineage
Simosuchus and the problem with living fossils
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