Creature Redefines Mammal History

Funny how the record turned up after DNA was interpreted to indicate the split was earlier than previously thought. <shrug> Life's like that.

The development from this point was explosive says a report hyperlinked from the above:

Land mammals went from small "vermin" to giant beasts in just 25 million years, according to a new study.

The modifier 'just' seems odd. 'Just' 25 millions years?

Okay, let's 'just' throw some numbers in the air to see what we get.

Suppose that the number of new species of mammals increases by 1 percent every 20,000 years. For humans, where there is approximately 20 years between one generation and the next, that would be equivalent to 1,000 generations. For many smaller species like the tiny mammals described in the article, there would likely be tens or hundreds more generations within that time frame.

A 1 percent growth in species over 20K years doesn't seem like a wild growth in numbers of new species, at least not to me. That would be the same as 1 percent more species of mammals on Earth since the peak of the last ice age.

So after 25 million years how many new species would there be? The number is staggering (I think): a factor of over 250,000. So if there were 1000 species of mammals on the Earth when the asteroid hit, then 25 million years later there would be over 250 million species of mammals. And some of those species would end up on the humongous-size end of the bell curve.

And at that same growth rate, over the entire intervening 65 million years since the asteroid impact, the number of species could have grown by a factor of 1.1x10¹⁴.

I presumed that it was "just" in comparison with the rise (and fall) of other types of animal - like the dinosaurs.

I think you also need to add to your calculation the rate of extinction, to see if the nett number of species matches those seen today, 8.7 million.

Thanks for the comments. Zoology is not my strong suit. _(Obvious?) I'm surprised there are 'only' 8.7 million species, of which 7.7 million are animals and 'only' about 6000 are mammals.

So I guess the rate of new species creation could be far less than 1% every 20,000 years; and with a moderate rate of extinction the 6000 number is easily achievable given even a hundred separate species of mammals 65M yrs ago.

_{/Gotta go do some research...}

No foul You made me think too...and look at what I just presumed from the report. Look forward to the fruits of your research...

<...research did suggest the existence of an upper ceiling to mammal body mass...>

Fast food companies beware!

It looks strangely familiar... just fluff out the tail a bit and hey presto
Del