Let's keep the loaded semantics out of the picture, shall we?
Homologies are by definition shared traits from common descent. So you cannot theorize about homologies not being shared traits.
You can discuss similarities that are considered to stem from common ancestry.
Not trying to be picky, but think the whole discussion can proceed better if we keep such terms out of the discussion.
Otherwise, we really have to decide if similarities should be called homologies, homoplasies, or neither (which is of course what we are trying to do here, but just to make a point).
Moreover, for convergent evolution to take place similar selective pressures must be in evidence.
That seems logical except that convergent DNA sequencing suggests otherwise. But it's an interesting point. If environmental pressures must be applied to create convergency, and we find examples of convergency that do not seem driven by environmental pressure, would that be evidence of a hidden environmental pressure such as an intelligent agent?
Why do birds show so many homologies with therapods when their lifestyles are so different?
Good point except we need specifics, and I have a question, are not the homologies advantageous for both groups of species? Assuming they are, that they are due to natural selection, why could they not be an example of convergent evolution?
Can a trait not be selected for, even when the 2 species have different lifestyles? You are assuming that the trait can only evolve independently from one set of circumstances, and that's just an assumption.
Plus, what if it did not evolve from convergency from outside selective pressures, but from convergent DNA, or ID (an intelligent agent), or just by golly, the same trait worked for both and independently evolved.
Could something like Archaeopteryx be the ancestor of later dromaeosaurs? I mean, maybe the dino-bird people see the whole thing backwards, assuming that because birds are with us here today and velociraptors are not, then it is concluded that birds are derived from the classic dromaeosaurs (Deinonychus, Velociraptor etal.) Which we all know imply a large gap in the dromaeosaurid fossil record back to the Jurassic.
thanks for answering my question....being that archaeopteryx has feathers and teeth i assumed that they would be a good transitional species between reptile and bird. but unfortunatly my creationist apponet could'nt see it that way.
if it was one of these so called 'transitional fossils' then it should have existed long before birds became a species, yes?
You seem to think that the ToE calls for a straight line descent, with each previous species dying out as the next species comes along. This simply isn't the case. At one point in time in the past, there were reptiles. Eventually, some of them evolved into birds, but that process took millions of years. During that process, there was an extended period of time during which reptiles, birds and their transitional intermediates all co-existed.
In essence, your argument is no different from the familiar, "How could we have evolved from apes if there are still apes around?" The only real perplexing thing is why you think you can make the same arguments over and over that have been refuted a thousand times and expect them to eventually convince anyone.
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quote:Are you referring to Archaeopteryx? Hasn't it definitely, especially with recent research, been found to be a bird?
It has a jaw with reptillian teeth, absent beak, a long bony tail, a neck that attaches to skull from rear (like dinosaurs) instead of from below (like birds), a flat breastbone, stomach ribs, reptilian vertebrae, unfused wristbones (birds have fused ones), unfused ankle bones (ditto), sacrum occupies only 6 vertebrae (half the minimum for birds), and (my personal favorite) three bony claws jutting out from the middle of each wing. These are reptillian characteristics, not bird ones.