Do you agree with these statements?

Kylie · Jun 27, 2020

klutedavid said:
Think it through. If the legs get shorter and shorter, when are they too short to run properly?

When do the fins start growing?

How does a swimming Zebra with very short legs catch anything in the water?

Why do you think that fins are required before an animal is able to survive well in the water? You do know there are intermediate stages, right? And they don't require long legs OR fins.

And why do you apparently think that only one trait can change at a time?

Radagast · Jun 27, 2020

Kylie said:
I honestly have no idea.

However, speciation requires reproductive isolation, and that may be geographical rather than biological.

The three currently recognised species of zebra (Mountain zebra, Plains zebra, Grévy's zebra) have different habitat preferences.

klutedavid · Jun 27, 2020

Radagast said:
The claim is that there were multiple chromosome-loss events.

See Speciation with gene flow in equids despite extensive chromosomal plasticity

Thus, we conclude that such massive karyotypic changes have not resulted in full reproductive isolation, in stark contrast with theories assuming that chromosomal impairment during meiosis is responsible for complete sterility in hybrids (18), but in agreement with the description of fertile offspring across equine species (32, 33).

klutedavid · Jun 27, 2020

Kylie said:
Why do you think that fins are required before an animal is able to survive well in the water? You do know there are intermediate stages, right? And they don't require long legs OR fins.

And why do you apparently think that only one trait can change at a time?

I don't see just one trait but say ten or more traits, that would be required. This is a very large set of physical transitions for a species to undergo.

I don't see how a Zebra with short legs could avoid getting bogged in the mud.

Where are the crocodiles? Hippopotamus are immune to crocodiles but Zebra are not.

Intermediate stages of what?

Kylie · Jun 27, 2020

Radagast said:
The three currently recognised species of zebra (Mountain zebra, Plains zebra, Grévy's zebra) have different habitat preferences.

And thus they are reproductively isolated, since members of one population are very unlikely to meet with members from another one.

Kylie · Jun 27, 2020

klutedavid said:
I don't see just one trait but say ten or more traits, that would be required. This is a very large set of physical transitions for a species to undergo.

I don't see how a Zebra with short legs could avoid getting bogged in the mud.

Where are the crocodiles? Hippopotamus are immune to crocodiles but Zebra are not.

Intermediate stages of what?

Intermediate stages from how they started to how the end up being well adapted to life in the water.

Radagast · Jun 27, 2020

Kylie said:
And thus they are reproductively isolated

Yes. One hypothesises that the original species event involved a similar isolation.

klutedavid · Jun 27, 2020

Kylie said:
Intermediate stages from how they started to how the end up being well adapted to life in the water.

Where are the predators?

Your transition is without the predators.

Kylie · Jun 27, 2020

Radagast said:
Yes. One hypothesises that the original species event involved a similar isolation.

Given that they are found in different areas, it seems likely that an ancestral zebra species spread out, and adapted to different environments.

You seem to be trying to suggest that there's no good cause to think that's what happened.

Kylie · Jun 27, 2020

klutedavid said:
Where are the predators?

Your transition is without the predators.

You seem to think that adding predators means that such evolution is impossible.

In my example I've tried to keep things simple because I'm describing the basic process, and I'm not intending to describe in detail how some real or hypothetical instance of evolution could take place. I'm trying to give an overview of the process itself. As such, I've kept it simple. In real life, there would be many genes controlling many traits, all of which are varying across the population, and there are many pressures acting on whether some individual survives or not.

The fact that I've kept things simple because the real life version is very complicated does not negate the plausibility nor the evidence supporting evolution by means of natural selection.

Job 33:6 · Jun 27, 2020

Kylie said:
Given that they are found in different areas, it seems likely that an ancestral zebra species spread out, and adapted to different environments.

You seem to be trying to suggest that there's no good cause to think that's what happened.

What's interesting is that Creationists tend to believe there used to be one horse "kind", so even for them it shouldn't be too hard understanding that zebras spread out and through geographic isolation took on their own unique traits. I'm not sure why they would have an issue with this idea now.

Radagast · Jun 27, 2020

Kylie said:
Given that they are found in different areas, it seems likely that an ancestral zebra species spread out, and adapted to different environments.

You seem to be trying to suggest that there's no good cause to think that's what happened.

Because it's quite possible that there was a speciation event producing 2 or more species, and that the adaptation to the existing habitats happened as a result of changes after that.

It is worth noting that the two most closely related species, E. quagga and E. grevyi, do have overlapping ranges, although E. grevyi is better adapted to arid areas. E.quagga (the plains zebra) also has slight range overlap with E. zebra (the mountain zebra). Range overlap of all 3 species may have been significantly greater in the past.

Job 33:6 · Jun 27, 2020

klutedavid said:
I don't see just one trait but say ten or more traits, that would be required. This is a very large set of physical transitions for a species to undergo.

I don't see how a Zebra with short legs could avoid getting bogged in the mud.

Where are the crocodiles? Hippopotamus are immune to crocodiles but Zebra are not.

Intermediate stages of what?

Pakicetus and earlier cetaceans were predators themselves, some with sharp triangular serrated teeth.

Predation has never mandated extinction of species, rather it's often considered a driving factor of evolution.

And crocodiles, assuming they were present at the time and place, wouldn't be roaming the Savannah like lions, so I don't think an early terrestrial cetacean having short legs would matter, as crocodiles wouldn't be hunting on land to begin with.

Kylie · Jun 27, 2020

Radagast said:
Because it's possible that there was a speciation event producing 2 or more species, and that the adaptation to the existing habitats happened after that.

That's pretty much what I said, isn't it?

A single group moves to different areas, becomes reproductively isolated, adapts to different environments?

Whether the actual evolution of the differences began before, during or after in no way invalidates the underlying principle I'm trying to describe in the OP, does it?

klutedavid · Jun 27, 2020

Kylie said:
You seem to think that adding predators means that such evolution is impossible.

In my example I've tried to keep things simple because I'm describing the basic process, and I'm not intending to describe in detail how some real or hypothetical instance of evolution could take place. I'm trying to give an overview of the process itself. As such, I've kept it simple. In real life, there would be many genes controlling many traits, all of which are varying across the population, and there are many pressures acting on whether some individual survives or not.

The fact that I've kept things simple because the real life version is very complicated does not negate the plausibility nor the evidence supporting evolution by means of natural selection.

You just pulled the ripcord.

Yes Kylie, it is a simple example but that is the problem is it not. The example you cited just doesn't really float.

Speedwell · Jun 27, 2020

klutedavid said:
I don't see just one trait but say ten or more traits, that would be required. This is a very large set of physical transitions for a species to undergo.

Not necessarily if they are related traits, as they evolve together. All of the traits are subject to constant randomly distributed variation and the selective environment for each trait includes the other related traits, not just the environment external to the creature.

Radagast · Jun 27, 2020

Kylie said:
That's pretty much what I said, isn't it?

A single group moves to different areas, becomes reproductively isolated, adapts to different environments?

Well, we have:

Hypothesis A (what you said): a single group becomes geographically spread (e.g. in mountains and plains), subgroups become reproductively isolated, and adapt to different environments, thus forming 2 or more species.

Hypothesis B (what I said): a single group separates into 2 species through some unknown mechanism (in the case of zebras, alterations to chromosome number may be involved with this), and after that the two groups gradually adapt to different environments.

An example of hypothesis B would be the distribution of wild horses and wild donkeys (burros) in the Americas. The species had diverged in the Old World before arriving in the Americas.

Distinguishing between hypothesis A and hypothesis B (speaking in general) usually requires extensive knowledge about the past.

Kylie · Jun 27, 2020

klutedavid said:
You just pulled the ripcord.

Yes Kylie, it is a simple example but that is the problem is it not. The example you cited just doesn't really float.

Given that you've demonstrated a bit of a lack of understanding about how evolution actually works, I have to wonder if you are in a position to justly say that my example is invalid.

klutedavid · Jun 27, 2020

Speedwell said:
Not necessarily if they are related traits, as they evolve together. All of the traits are subject to constant randomly distributed variation and the selective environment for each trait includes the other related traits, not just the environment external to the creature.

But your talking about millions of years of gradual variation. Any species transforming from a tetrapod to a infraorder Cetacea, is extremely vulnerable during that slow transition. Mainly because it cannot swim or run properly during that transition. Regardless of how many traits are developing.

This profound transition is impossible.

Kylie · Jun 27, 2020

Radagast said:
Well, we have:

Hypothesis A (what you said): a single group becomes geographically spread (e.g. in mountains and plains), subgroups become reproductively isolated, and adapt to different environments, thus forming 2 or more species.

Hypothesis B (what I said): a single group separates into 2 species through some unknown mechanism (in the case of zebras, alterations to chromosome number may be involved with this), and after that the two groups gradually adapt to different environments.

An example of hypothesis B would be the distribution of wild horses and wild donkeys (burros) in the Americas. The species had diverged in the Old World before arriving in the Americas.

Distinguishing between hypothesis A and hypothesis B (speaking in general) usually requires extensive knowledge about the past.

Of course, either one is possible. I wasn't intending to imply that there was any particular evidence that it MUST have happened the way I suggested. Like I said, I'm just trying to keep things simple here, and trying to explain all the different possibilities could have made things confusing for people who are unfamiliar with evolution.

Do you agree with these statements?

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