Re: Carnivore Energetics: Why Are Lions Not As Big As Elephants? .. and why aren't antelopes?

[john bois <jbois@verizon.net>]

>3) given the above environmental conditions and body size, there is the
added advantage (or logical consequence) to favor the
'run-away-from-predators' approach as a survival strategy, instead of hiding
or fighting;
>4) given survival strategy in 3), it makes sense to carry one or a few
large young with you as a reproduction strategy, in stead of hiding or
defending a large nest of small offspring;

>From the point of view of the mother's escape, it doesn't really matter if
you have 2 small babies or one big one.  But one baby gets more placental
resources (i.e., can grow bigger/smarter/faster before birth) and has
therefore a real advantage over two less developed offspring when _it_ has
to face the day.  Also, though we can't be sure, it is likely that
smarts/sensory acuity, and not speed, was the adaptive advantage enjoyed by
our very small ancestors.  So, I'm arguing that increased parental
investment leading to better prepared offspring--whatever that meant in a
particular environment--has negated the need to be big.
And even extant largish dinosaurs try to maximize offspring readiness
with--in the case of emus--extended incubation times.  But for them this
means hiding--usually grass is a component of their cover--or being very,
very secretive.  For sure, without grass and with the imperative of guarding
an easily visible nest, things were very different for earlier dinosaurs.  I
believe they were under a tyrannical selective pressure not felt at all by
placental mammals.