No, it’s not really strange when you consider that from about starfish/sponges onwards, animal evolution adopted a bilateral symmetry in its embryonic development.
That's a circular argument, evolution did not evolve 3 limbed animals because in the past evolution did not evolve any 3 legged animals!!
It's not really an argument or explanation at all, it's basically repeating the question but omitting the 'Why' at the start!!
The question why, saying that is how is it is not any answer!!
That's a circular argument, evolution did not evolve 3 limbed animals because in the past evolution did not evolve any 3 legged animals!!
It's not really an argument or explanation at all, it's basically repeating the question but omitting the 'Why' at the start!!
The question why, saying that is how is it is not any answer!!
It is a circular argument.
If I said why are their no palm trees in Antarctica saying "Well there have never been any there", is a pretty poor answer.
I am not shifting the goal posts, the exclamation marks are for the lameness of the answer.
You can answer any question with such flippant answers.
You might as well say because there aren't any!!
are there any odd numbered limbed creatures?
are there any odd numbered limbed creatures? insects have 6, octopus have 8...
No it isn't.
Oh, and incidentally...
Bathypterois grallator:
Strange there are none.
No it isn't.
Oh, and incidentally...
Bathypterois grallator:
Note that it is balancing itself on modified fins.
Also note, that we could consider a prehensile tail in the same way.
The point being that odd numbers of limbs (like a starfish) requires radial symmetry, with the body segments arranged around a central axis. All the higher animals that we know of use bilateral symmetry - essentially the body segments are arranged along a central axis.
The only way to get an additional (odd) limb would be as an extension of the central axis - IE a prehensile tail.
You seem to assumed bilateral symmetry is a God given thing but you have failed to explain why.
I am surprised at how many people think this kind of answer is a valid one.
Contrary to conventional wisdom, four axes likely provide the 'coordinate system' by which cells recognize their location:
one antero-posterior axis ("head-to-tail"),
one dorso-ventral axis ("top-to-bottom"), and
two medio-lateral axes ("distance from the midplane"), one on each side of the body.
With this information, however, a cell cannot tell whether it lies on the right or the left side of the midplane. It only knows how far it is from the head end, from the top side, and from the midplane. Therefore bilateral symmetry may simply be a default: the absence of any symmetry-breaking information. For the left side to diverge from the right developmentally, additional positional information is required.
Many animals have five limbs (two arms, two legs, tail.)
No, it’s not really strange when you consider that from about starfish/sponges onwards, animal evolution adopted a bilateral symmetry in its embryonic development.