Evolution: How much change is required to become a new species?

We have seen that a species can change within 35 years to adapt to a new environment when an insect eating lizard was taken to a place where he had to learn to eat plants....

How much change do you think any species would have to go through to cross over from one species to another?

Like fish to a lizard.

Does the theory of evolution have progressive evidence of a change like this?

I'm not an expert on the new (or even the old) theory.

Many philosophers of science have claimed that evolutionary is a ‘merely explanatory’ science, rather than a predictive science

"when pigs fly"


something like that...

The very notion of species is a man-made concept.

It is simply defined in terms of whether or not two creatures can interbreed naturally and produce offspring that can also procreate in a similar manner.

That's a man-made definition of what we mean by 'species'. We arbitrary used that distinction to define this term.

So if you take a group of a single species and slit that group up on two isolated islands for a long enough period of time they will eventually diverge to the point where the two groups will no longer be able to procreate viable offspring.

Then you are justified in stating that they are no longer the same species.

Precisely how many generations that will take to achieve is something that a geneticist might be able to answer.

Obviously you'll have far better luck using species that procreate quickly and die quickly. That way you can observe many generations over a short period of time.

If you use elephants for your experiment you probably won't live long enough to see any change. I think a single generation for an elephant is longer than a human lifespan.

So better off using fruit flies or something like that.

In fact, I think there have been biological experiments where this has actually been achieved. But arguments then arose concerning whether or not they had actually created a new "Species".

Let's not forget that the very definition of "species" is a man made construct. We simply define "species" based upon an ability to procreate between the same creatures.

That's a totally arbitrary definition and term created by man.

If these fruit flies can no longer breed with those fruit flies does that really mean we have created a new "species"?

They both still LOOK like Fruit flies to me!

Just because they have sexual impotency problems doesn't mean they are a new species!

That's the argument that is given against these kind of experiments.

The whole notion of what it means to be a "species" comes into question.

Exactly. That's what people want to see.

They aren't interested in fruit flies that can no longer breed with another group of fruit flies.

They wants to see pigs with wings!

Or the mystical unicorn brought into reality.

How many cases do you think can be found where to different types of animals or insects did breed and create a different animal or insect?

Like spiders, etc.

I know they have created first generation crosses, but wasn't there a case where a mule had an offspring?

http://www.denverpost.com/headlines/ci_6464853

saw an old cosmos episode with carl sagan the other day. he was giving his take on evolution. told a tale that took place in the 1300s in samurai ruled japan. a clan of samurai was anialated by a rival clan. at some point a crab was found that had an image on it's shell that resembled the face of a samurai warrior. when such a crab was caught it was thrown back in honor of the lost clan. a crab without the image would be consumed as food.

after a time more and more crabs were being caught with this now sacred image on it's shell and were all thrown back to live out there lives. today the vast majority of this particular crab species bears the samurai image. coincidence or have these crabs evolved in such a manner that better enhances their chances of survival?

Survival of the lucky samurai crabs.

I remember having watched that documentary many years ago.

I totally agree with the concept there and how traits can indeed be controlled by natural selection.

However, in that particular case, the crabs are still just crabs and the ones that have samurai makings on them can probably still breed with crabs of the same species that don't have those markings.

So no "new species" was actually created due to that process.

But it does show how traits can be selected over time.

But we already know this from looking at all the different breeds of dogs that mankind has bred. Yet they are still all dogs.

Although, I'm not really sure whether a dog can procreate with a wolf?

Does anyone know whether dogs and wolves can breed successfully? I mean assuming they survive having intercourse of course.

Are dogs and wolves totally separate species now?

If they are, then isn't that an example of where mankind created a "new species" from a preexisting one?

Dogs and wolves can procreate, and I think their offspring can also. They are the same species.

A wolfdog (also called a wolf–dog hybrid or wolf hybrid) is a canid hybrid resulting from the mating of a wolf (various Canis lupus subspecies) and a dog (Canis lupus familiaris). The term "wolfdog" is preferred by most of the animals' proponents and breeders because the domestic dog recently was taxonomically recategorized as a subspecies of wolf.

The American Veterinary Medical Association and the United States Department of Agriculture refer to the animals as wolf–dog hybrids.[1] Rescue organizations consider any dog with wolf heritage within the last five generations to be a wolfdog, including some established wolfdog breeds.[2]

Lions and tigers can procreate with each other but what about their offspring?

****


>Yes a liger can reproduce.Female ligers are often fertile and can be mated to a tiger resulting in ti-liger offspring or to a lion resulting in li-liger offspring. A behavioural research program in the USA has bred a female ti-liger called Lady Kali. At 2 years old she weighed 400 lb (180 kg).

>Known male ligers have all been sterile. Many, however, reach sexual maturity and copulate with lionesses, tigresses or with female hybrids. A. H. Bryden reported in "Animal Life and the World of Nature" (1902), Already, I understand, Mr Hagenbeck has mated the big lion-tiger hybrid with other pure-bred felines, but with no result. This referred to the liger bred in 1897.

Well, I'm not surprised by that. Dogs and wolves are highly complex animals that have fairly long generations. It would take quite a long time before they will evolve to the point where they can no longer breed.

Like I say, if you want to see evolution in action you're going to need to use a species that has a really short lifespan and can have many generations in a fairly short period of time, and even then it's going to take many many generations to get to that point.

So I really wouldn't expect to see this between dogs an wolves. They are far too closely related yet. They simply aren't enough generations apart yet. Give them enough time and they eventually will be. But it make take tens of thousands of years.

After all, evolution itself has had millions of years to work with.

carl suggested that is wasn't natural selection but artificial selection in that humans caused the change. and, it was not a new species.

Hybrids.....

http://ufocasebook.com/alientypes.html

Ok Ok,

What do you get when you cross a Donkey and an Onion?


Virtual Beer to first correct answer.

Are you suggesting that humans are artificial?

If birds that feed on crabs had passed by all the crabs that had weird markings on their backs would what have resulted in 'natural' selection?

never did i suggest anything. said carl suggested that the crab mutations were the result of artificial selection.

Well, it seems strange to me that human activity should be considered to be "artificial".

Are humans considered to be artificial?

Maybe Carl just chose a poor term.

Perhaps he should have simply said "Human selection" rather than "artificial selection".

I understand what he meant. But technically he is basically implying that human activity is somehow 'artificial'.

Why shouldn't human activity be considered to be just as 'natural' as any other activity?

afraid you'll have to perform the impossible and take it up with carl.

Right.

There were two things at work in the crab incident.

1. The crabs without the design were eaten by a huge hungry population of humans.

2. The crabs with the design were thrown back to reproduce.

It is only logical that the crabs with the design would increase and the ones without the design would diminish.