Question: Hi Vera, Do you know of any evolutionary benefits of not being able to generate and regulate your own body heat - as happens in reptiles. What advantages are there of relying solely on the sun, save for conservation of some energy? There seems to be much time wasted by organisms warming up, which could be spent foraging, hunting, or activities that are more evolutionary effective. Thanks

Vera Weisbecker answered on 17 Jun 2011:

Great question and you are actually spot on – there is a lot of time being wasted by animals who can’t generate their own heat for exactly the reasons you mention. Being dependent on external heat sources is actually not an adaptation at all – the “default” of all living organisms is that they can’t produce heat. Only two groups of vertebrate animals – birds (and perhaps their relatives, the dinosaurs) and mammals – have evolved the ability to heat themselves. And that has enabled them to live in places like the arctic and antarctic, or run around at night when reptiles and amphibians are too cold to move.