Biology Forum Evolution Marine Invertebrates and Evolution

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    • #13190

      I was watching this debate:

      Around 7:00, Philip Johnson claims that the fossil record marine invertebrates is one of the most complete, yet there aren’t any transitional forms (or perhaps too few). Even though I can’t stand these reality denialists, it does seem like a valid point (for once). However, I dont’ know much about paleontology, so I thought I would start a discussion here to see how biologists will respond.

    • #99341

      For reasons having to do with sediment and other stuff I don’t completely understand, marine environments are much more "fossil-friendly" than other places, so it is indeed the case that the majority of fossils are of marine animals.

      However, it is not correct that we lack marine transitionals — to the contrary, most "obviously transitional" fossils are marine, in an equivalent proportion to the "obviously transitional" terrestrial fossils. Here’s just one grouping of them — the fossil gastropods; … sil_record . It’s a looong list, and they all fit in a nested hierarchy of transitionals.

      I imagine that what Johnson means is that the fossil record lacks predecessors to the earliest marine animals. To some extent, however, this, too, is to be expected. Nearly every single known fossil is of a hard-bodied creature (for obvious reasons) and hard-bodied creatures first arose in the water. The predecessors to these organisms would, at some point, fall below the hardness threshold for fossilization to be likely. Similarly, our record of fossil insects isn’t nearly as complete as we’d like it to be. Should we say, "Well, clearly, insects just popped into existence"?

      Now, I hate to do a tu quoque, but in this case, I can’t resist. Phillip Johnson is quite likely a YEC; at least, he’s never denied or argued against YEC ( … son-1.html ). Now, if one uses the old Cambrian explosion argument, one has immediately discarded any possibility of literal creationism. Why? Because the fossil record doesn’t indicate the simultaneous deaths of every "kind" on one single stratum, corresponding to either the beginning of death after the Fall, or to the massive death which would follow the Flood. In order to argue using the Cambrian explosion, you have to either accept that all those mollusks/gastropods/etc were "created" long before, for example, the tetrapods, or that the fossil record is actually meaningless (which means you can’t use it in your arguments).

    • #99366

      The best examples are micro-organisms. To follow an evolutionary pathway closely, you need lots of fossils. To get these, you need something that is present in vast numbers, and leaves hard remains that will fossilise. The radiolaria and the foraminifera are micro-organisms that meet both conditions. Micropaleontologists have uncovered a number of evolutionary pathways for these organisms that are exquisite in their detail of how the organisms changed over time.

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