the most observable results of evolution from species A to species B are the physical differences between adults of species A and B. this is due mainly to one driver of evolution which is sexual selection. sexual selection is done at mating age. similarly, competion for other commodities such as territory and food is usually observed among adults. infants and juveniles often have “inconsequential” features that disappear with maturity. an example would be the “watermelon” stripes in young wild pigs that disappear. more improtant would be tusk size and overall body size which would be important features at adulthood. fetuses of species within a genus or even a family can be strikingly similar. finally, offspring may mature into animals with features different from all its progenitors.
therefore, i feel that the first chicken was hatched from a non-chicken egg, by non-chicken parents.
It’s not as binary as chicken/not-chicken. There’s a 1% chicken which lays an egg that hatches into a 3% chicken wlaethia 5% chicken wlaethia 12% chicken wlaethia … 100% chicken. A chicken’s immediate ancestors aren’t “not chicken”, they’re “95% chicken” the way Homo heidelbergensis was 95% human
Not really - I mean, you get lots of species where the adults are reasonably indistinguishable but it’s the behaviours (both juvenile and adult) and intrinsic makeup that are different.
Superficially, American and European Eels are very alike as adults, but their chromosome counts differ and they’re already distinguished at the larval stage by which coast they’re going to head for.
Let’s say they’re a useful first draft, but the state of the art has moved on to genetics, and as tech improvements has made it easier, genome comparisons etc seem to be the way to go. But there’s always going to be a use for live observation too.
Note that this is much more the case for animals. For plants genetics gets a lot more… complicated.
For that matter, current chickens are not 100% chicken. Evolution is not a process with an end state. All organisms change over time, speciation is still occurring. Each generation of chickens is different than the one before, albeit in inconsequential ways.
Some animal was the first chicken. So its parent was not a chicken. So a non-chicken laid an egg out of which hatched a chicken. Was the egg a chicken egg? Take your pick. If you think it’s better to name an egg after what laid it, then no. If you think it’s better to name an egg after what comes out of it, then yes.
No; a population of birds over time bit by bit evolved away from the ancestor species of chickens. It wasn’t one bird, and it wasn’t any sudden jump from not-chicken to chicken.
Could be, but not necessarily. Species designation, at that level, is entirely arbitrary. A human construct that can be defined in many different ways. We may choose to define the non-chicken -> chicken speciation event that way, but there is no objective reason for doing so.
Sometimes ambiguity isn’t necessarily wrong.
And, in fact, the way we do designate species (The Biological Species Concept) would almost certainly not work the way you describe, as it would require one generation of a population to not breed with the previous one.
I think that we’re forced to define eggs in terms of what laid them rather than what hatches out of them. Else, what would you call those eggs I bought at the grocery store last week? They’ll never hatch into anything.
Your assumption that sexual selection is the driving force behind the speciation event that gave rise to the modern chicken is nothing more than unsupported speculation. Sexual selection is one of several driving forces behind evolution. There is no a priori reason to assume that it is the primary force in this case. Your attempt to make a link to juvenile/adult dimorphism is confusing at best and completely nonsensical at worst.
That’s a good point. Sexual selection is an important driver of evolution, but you usually see that in terms of elk antlers or peacock tails. What type of egg gets laid doesn’t seem to scream out “sexual selection”. How would the cock know what type of egg the hen is going to lay before he did his cock thing, anyway?
If you take modern chickens, I’m sure you’d judge them as chickens. But now, let’s go back a thousand generations, and they look a little different.
Me: Here’s an ancestor from 1000 generations ago. Is it a chicken?
You: Yeah, clearly, even though it looks pretty different.
Me: Here’s an ancestor from 10,000 generations ago.
You: Yeah, that’s kinda funny-looking, but I can tell it’s still a chicken.
Me: Here’s an ancestor from 20,000 generations ago.
You: Well, it’s chicken-like.
Me: 30,000 generations.
You: It has some characteristics that I can tell would lead to chickenism.
Me: 40,000 generations.
You: Well, that’s not a chicken. It’s a bird, but not a chicken.
Now, at what exact point in that line would you say that the birds had changed to fit your exact definition of “chicken”? Is your definition of “chicken” so exact that you can say that, for example, the one from 21,347 generations ago was not a chicken, but the one from 2,436 generations ago was a chicken?
Do you really think that definition of “chicken” that you have in your head is precise enough to place a divider there?