Is there a scientific reason why larger animals, such as mammals, can't or don't have 6 legs like an insect?

Question

If you have a source, for an scientific hypothesis, about why this doesn't happen in higher forms of life, please post it.

Answer 1

Mammals and all land vertebrates evolved from Coelecanthe fish which were originally bottom feeders sort of like catfish of today. They had four stubby fleshy fins to help them move along the bottom where they lived. This allowed them to be the only fish that even had a half of a chance of survival when attempting to crawl onto land, since they had something to propel themselves with, however clumsily. Insects probably evolved from centipedes, losing all but six limbs because such loss made them faster and better able to escape predation. It seems that four to six limbs is close to the ideal number, since one group (Vertebrates) came up to four from zero while another group (insects) came down from ~100.

Answer 2

It's not just the "large" animals ... but *all* terrestrial vertebrates are tetrapods ... this includes mammals, birds, dinosaurs, reptiles, and amphibians ... all of which (except for dinosaurs) have some pretty tiny members that are smaller than some of the larger insects.

The scientific reason is quite simple ... this is explained by the idea that they all descended from the same ancestor (a species of lobe-finned fish).

It's not so much that they "can't" have extra legs, just just that there has never been an evolutionary event that caused additional limbs (although, in the case of snakes, some limbs have been lost ... although you can still find vestigial leg bones in the skeletons of some snakes).

P.S. Watch out for that language "higher forms of life." Biologists once used that as a carry over from the day we thought that "up" meant "more advanced" ... i.e. "closer to humans" ... but biologists try to avoid that way of speaking now. Evolution makes much more sense if you think of it as a branching bush, not an upward chain of one animal evolving into a "higher" form.

Answer 3

Evolution

Answer 4

we have fingers so we don't need the extra legs and a different type of skeleton ours is on the inside and theirs the outside and called an exoskeleton so their distrubution of weight on their bodies is more side to side than vertical like humans so the extra
legs help the exoskeleton be balancedl

Answer 5

Mammals are terrestrial lungfish whose ancestors happened to have four limbs. So mammals are evolutionarily constrained to only four limbs.

Or to put it another way; "because."

Answer 6

no the only one is because God made it that way