Is there a correlation between fossil record and population size?

At least at first glance, it seems there some correlation between the appearance in the fossil record and the number of species per taxa. which might mean that the fossil record just represent population size (more species= more chance to leave fossils). so here is the estimated number of species for some groups, and this is also their order in the fossil record:

bacteria -10^30 individuals
algae- 3000000(?)species
plants -320000
mollusks -100000
reptiles -10000
birds -10000
mammals -5000
primates -500
cats -40
human -1

note that we should not expect to find a perfect correlation (for a few reasons im not going to elaborate right now), just a general one.

No use trying to argue about an idea where you haven’t actually shown a correlation. We have no idea whether your organisms were simply cherrypicked or suffer some other kind of sampling bias.

Since you’ve now thrown out this excuse that “note that we should not expect to find a perfect correlation”, there’s no use even bringing up contradictory examples since you’ll just jump straight to this handwave every time.


Population size is not the same as nor necessarily correlated to number of species. Current number of species isn’t the same as the total number of historical species, which is what would be relevant to the fossil record. So this is doomed to failure.

Also, mammals preceded birds. If you don’t even know that, you don’t have the knowledge to even start such an analysis, and should go and learn stuff first.

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What? That sentence is a non-sequitur and a failure of math and logic.

Population size is not proportional to number of species; in fact, with the creationist model with kinds diversifying over time, the population size of a given species is probably inversely proportional to the number of species present under creationism.

In fact, if originally there was a limited number of ancestral created kinds, there would be a higher density per unit area of each of the ancestral kinds before they diversified; that is, we should find MORE ancestral Equus kind fossils, MORE of the ancestral Girrafid kind, MORE of the ancestral pair or seven pairs of kinds that were on Noah’s Ark.

(And of course, a difference in genetic diversity of the “unclean kinds” vs “unclean kinds” in the creationist model).

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true. but it should give us a clue about the past.

not according to this source:

note that we are talking here about “true” mammals, which is about the same age for the oldest “true” birds like the archaeopteryx and probably also aurornis. and if we include the problematic protoavis, then there is no real problem. we also need to remember that the fossil record of birds is a bit problematic, probably since birds have hollow bones.

So you want to limit mammals to “true” mammals (i.e. ignore non-placental ones), but also want to extend birds back to problematic controversial fossils.

I don’t accept your blatant double standard.

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We probably have more fossils for T. rex, which is a single species, than we do for the 20,000 extant and innumerable extinct species within the phylum Platyhelminthes.


As far as I know, there are zero platyhelminth fossils. There are a few eggs found in subfossils, but that’s it.

and yet they appear earlier than the T. rex in the fossil record. anyway, since worms dont have bones at all, and since they are very small ( and thus can be easily eaten by other animals), the chance for them to leave fossils should be smaller than other animals.

Can you document that?

Aha, so you agree that there are taphonomic biases in preservation. That destroys your thesis right there.


Then, three days later:

There you go. Spend enough time thinking about it, and often one figures out the silly blunder one made. A valuable lesson for us all.


i even said that in the first post (“we should not expect to find a perfect correlation”). anyway, what is your explanation for why we find the organism with the largest population (bacteria) first in the fossil record?

Because for several billion years there weren’t any other organisms. Of course, most sorts of bacteria aren’t represented in the fossil record. And anyway, it’s mostly not the bacteria themselves but the structures that result from undisturbed cyanobacterial mats, stromatolites.


I’m having a hard time following your logic here, such as it is. If the population of one organism is much greater than that of another, all else being equal we would expect its fossils to be more plentiful at whichever stratum we looked. There is no reason to expect its fossils to be found earlier.

Could you clarify?

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Yes there is. The more plentiful a species is, the more likely we are to have found at least one specimen so far, and the closer the first fossil appearance would be expected to be to the real first appearance of the species, all things being equal. But of course the pattern @scd claims to see doesn’t really exist. He’s relying mostly on a single data point, that the earliest fossils are of bacteria.

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Bats are the one of the most numerous orders of mammals, and yet they aren’t the first mammals to appear in the fossil record.

OK, that makes sense.

ok. but what does this have to do with the size of their population?

how many bats are there?

I’m a little disappointed that people read the OP and felt that it merited a response.

Of course, now I’m disappointed in myself too. Having said that, would anything of value be lost if we let this slip off the front page into obscurity?