Evidence that mammals evolve to be smaller during warm periods

http://phys.org/news/2013-11-global-dwarfism-mammalstwice.html

Makes sense: assuming the body shape doesn't change all that much, the larger the warm-blooded body size, the less the body volume to surface area ratio and the lower the rate which it looses heat; good for cold climates but bad for hot climates. Thus, at least for warm blooded animals, natural selection would generally favour a smaller body size in hotter climates than in colder climates.

But I have just two criticisms of this link;

1, the link failed to explain the above explanation so that laypeople would understand why this evolutionary phenomenon should happen. I would guess that far from all laypeople would work that one out for themselves so I think that they should have mentioned it. The link even says "Interestingly, the extent of mammalian dwarfism may be related to the magnitude of the hyperthermal event," as if they were surprised by this observed evolutionary phenomenon! Surely they didn't fail to see the simple reason why that observed evolutionary phenomenon should happen!? If so, shame on them.

2, the link uses the scientifically obsolete Fahrenheit scale for temperature; That's pretty silly of them.

Originally posted by humy
Makes sense: assuming the body shape doesn't change all that much, the larger the warm-blooded body size, the less the body volume to surface area ratio and the lower the rate which it looses heat; good for cold climates but bad for hot climates. Thus, at least for warm blooded animals, natural selection would generally favour a smaller body size in hotter climates than in colder climates.

Another big factor is availability of food vs population of predators. Generally bigger is better for fighting of predators, but smaller is better when food is scarce. The scarce food effect is what is cited in the article (last two paragraphs).
It is well known that mammals trapped on an island with no predators quickly get smaller.

And some mammals evolve to be bigger.

I am thinking of Insectivora:s. (Mammals that only eat insects). Because when it is warm insects grow bigger. Then their predators also follow that pattern. As is the case with this little fellow here. (Living in Africa).

http://www.sciencedaily.com/releases/2008/02/080201085759.htm

http://en.wikipedia.org/wiki/Macroscelididae

Originally posted by twhitehead
Another big factor is availability of food vs population of predators. Generally bigger is better for fighting of predators, but smaller is better when food is scarce. The scarce food effect is what is cited in the article (last two paragraphs).
It is well known that mammals trapped on an island with no predators quickly get smaller.

Generally bigger is better for fighting of predators, but smaller is better when food is scarce.

yes, agreed. But I don't see how that could explain why this would cause mammals to grow smaller when climate becomes hotter because hotter climate doesn't necessarily mean less food and can mean more food! So I don't think that would be a very good explanation in this particular case.
The link says:

“...Gingerich proposed that mammalian dwarfing could be a response to the lower nutritional value of plants grown under elevated carbon dioxide levels. Under such conditions, plants grow quickly but are less nutritious than they would normally be. ..”

but the plant food being less nutritious doesn't mean there is a shortage of such plant food. And, if and where there is no shortage of such plant food, but that food becomes less nutritious, but, lets say, hypothetically, the temperature of the climate stays the same (this hypothetical is just for the sake of argument to make all else equal ), I would expect the herbivorous mammals to grow larger, not smaller, in the response to that plant food being less nutritious! This is because larger means the body can support a bigger mouth and gut to digest it and so the animal would be able to eat more of it but the amount of energy needed from the food per gramme of mammal body weight to keep the mammal sufficiently warm would be less if it is larger because it would not be loosing heat so rapidly because of the lower volume to surface area ratio.
Also, I have heard somewhere (don't remember where ) that the work done by microbes in a herbivorous gut generally tend to do a better job at helping to extract more energy out of the plant food when that gut is larger (not sure why that would be true ) . If that is correct then I think surely a larger gut needs a larger body to support it.

Originally posted by humy
If that is correct then I think surely a larger gut needs a larger body to support it.

You make good points for why animals might get larger, but now you need an explanation for why animals would get smaller.
I believe smaller animals mature earlier, require less resources to get to maturity and reproduce faster. This is an advantage whenever there is no reason to grow larger.
It would be interesting to know what parts of the world they did the study for. In the tropics, large body size to retain heat is probably not important (yet there are plenty of large mammals).
Also, during the time of the dinosaurs, the earth was much warmer than it is now, yet they grew much larger.

Originally posted by twhitehead
You make good points for why animals might get larger, but now you need an explanation for why animals would get smaller.
I believe smaller animals mature earlier, require less resources to get to maturity and reproduce faster. This is an advantage whenever there is no reason to grow larger.
It would be interesting to know what parts of the world they d ...[text shortened]... the time of the dinosaurs, the earth was much warmer than it is now, yet they grew much larger.

smaller animals mature earlier, require less resources to get to maturity and reproduce faster.

Good point. Haven’t factored that in.

Also, during the time of the dinosaurs, the earth was much warmer than it is now, yet they grew much larger.

arr yes, but dinosaurs were probably cold blooded I think (I not sure if I buy the theory by some that they were warm blooded ) so not all the same reasoning would apply for them as with mammals.

Originally posted by humy
http://phys.org/news/2013-11-global-dwarfism-mammalstwice.html

Makes sense: assuming the body shape doesn't change all that much, the larger the warm-blooded body size, the less the body volume to surface area ratio and the lower the rate which it looses heat; good for cold climates but bad for hot climates. Thus, at least for warm blooded animals, natural s ...[text shortened]... uses the scientifically obsolete Fahrenheit scale for temperature; That's pretty silly of them.

The worldwide flood.

The Instructor

Originally posted by RJHinds
The worldwide flood.

I may regret asking this but;
what the HELL do you think is the relevance of the mythical world flood has with explaining why mammals evolve to be smaller in hotter climate?

Originally posted by humy
I may regret asking this but;
what the HELL do you think is the relevance of the mythical world flood has with explaining why mammals evolve to be smaller in hotter climate?

It obviously resulted in a drastic change in the biosphere and climate control that should effect the growth and survivability of the remaining living creatures.

The Instructor

Originally posted by RJHinds
It obviously resulted in a drastic change in the biosphere and climate control that should effect the growth and survivability of the remaining living creatures.

The Moron

that vagueness doesn't answer my question.

Originally posted by humy
that vagueness doesn't answer my question.

Lack of nutrition and stress from the elements can effect creatures in various ways. The conditions of the earth after a worldwide flood would not have been as beneficial to living things as they were before. The lack of the best food is likely to result in animals not reaching their maximum growth potential. Excessive radiation and extreme cold could have detrimental effects that might even extent to the DNA.

The Instructor

Wouldn't it be cool if all plants, animals and humans were scaled down to where people were only an inch tall? The earth would sure be a lot bigger in our minds eye.

Originally posted by joe beyser
The earth would sure be a lot bigger in our minds eye.

I don't think it would. Our minds eye simply cannot take in things as big as the Earth. If you were in Google earth it would only make a difference of about have a turn of the mouse scroll when zooming in or out. You simply wouldn't notice it unless someone told you.

Originally posted by RJHinds
Lack of nutrition and stress from the elements can effect creatures in various ways. The conditions of the earth after a worldwide flood would not have been as beneficial to living things as they were before. The lack of the best food is likely to result in animals not reaching their maximum growth potential. Excessive radiation and extreme cold could have detrimental effects that might even extent to the DNA.

The moron

Replacing one vague statement with just a load more doesn't answer my question -read my question again and came back to us. Also, flooding doesn't cause "Excessive radiation" so you are making absolutely no sense whatsoever anyway.

[off topic]

I have just installed BG script and the first thing I did with it is block all posts from RJHinds so that they are now completely invisible to me!
This is an inferior substitute to my proposal of making a "Religion VS Science" public forum but, still, I will give it a good go.

I have already noticed that this forum looks very different now! So nice to not see all that load of crap from the moron for a change!

possibly my last ever message to RJHinds;

Don't bother to get my attention now (or you can try if you like! -its your time to waste! -go right ahead! -SHOW everyone else just how STUPID you are!!!! ) because I can't see ANY of your arrogant condescending delusional moronic posts any more! Not even, I have noticed, when one is the OP of a thread!
Yippee!

Anyone; Is anyone here in the Science forum also using BG script? just curious.

[/off topic]