5
votes
0answers
32 views

Why are recombination rates increasing in mammals?

I have recently become fascinated with an awesome topic in biology and evolution that I feel is rarely covered in biology courses. That is, rates of meiotic recombination, or the the amount that an ...
1
vote
1answer
73 views

Has any creature ever devolved to be cold blooded? [closed]

Is this even possible? Because I have a non-scientific gut feeling that it is irreversible. Whales and dolphins are evolved from land mammals, and they've remained warm blooded while it doesn't give ...
0
votes
0answers
32 views

How important is the womb's environment?

Background Talking about one particular phenotypic trait, the total phenotypic variance $V_p$ is decomposed into genetic and environmental variance for this trait, represented by the symbols $V_G$ ...
2
votes
1answer
104 views

Why haven't land animals evolved beyond urination?

It occurred to me (while urinating) that this would seem to be selected against because water is a scarce resource. Why are we constantly losing water we don't need to through urination? What is ...
3
votes
2answers
498 views

The number of nipples (breasts) a species has?

Only mammals have mammaries and mammary glands. What evolutionary factors determines the number of mammaries (nipples/teats/breasts) a species has? Is it always an even number?
1
vote
1answer
131 views

Cats, Dogs and Bears - how are they related?

What is the ancestral relationship between cats, dogs and bears? I presume they are more closely related to one another than other paraphyletic clades of mammal. Which came first? What did their ...
6
votes
5answers
866 views

Why do most mammals have long snouts?

It seems like most mammals, e.g. dogs, have long snouts. My pet dog's snout would seem to me like an evolutionary disadvantage, since her canine teeth are way out at the end of her jaw, which acts as ...
3
votes
1answer
377 views

Why do sloths come down from the trees to defecate?

I'm under the impression that most sloths exhibit this behavior, but why? They are slow moving and so have no way of escaping from predators when on the ground. Not to mention the energy they expire ...
4
votes
1answer
169 views

Birds from the Family Columbidae Feed Young “Crop Milk”

Birds from the family Columbidae (e.g., doves and pigeons) produce a fatty, milk-like substance in their crop. The secretion is often referred to as "crop milk." They feed crop milk to their young ...
5
votes
1answer
130 views

What selective factors drove the evolution of lactose in lactation?

As far as I can determine, lactose, and the monosaccharide galactose have few biological uses outside of mammalian lactation. It not only required enzymes for its production, but enzymes in offspring ...
6
votes
1answer
3k views

Why can't humans drink sea water?

Why can't humans drink sea water? It would seem to be a huge evolutionary advantage for an animal to be able to drink sea water rather than have to rely on fresh water, and it's provably not ...
5
votes
1answer
130 views

Why was polyploidy not lethal in certain octodontid rodents?

As discussed in Why is polyploidy lethal for some organisms while for others is not?, polyploidy is normally lethal in mammals. However, two species of Octodontidae (South American rodents), are ...