Origin of Species

[Binkie]

Just had a thought about Jonti's Herring Gulls and Blackbacks. Can Herring Gulls and Blackbacks interbreed? Or are they separate species? If so, where around the world does the species-change occur?

 

[Crispy]

Yes I do.

See what you mean. So there's a question there then. Who's morphed the most?

Hard to tell. Ask a biologist. There's ways of estimating it, invovling mutation rates etc. But it's an inexact science, AFAIK. This is where you need a library

 

[Jonti]

Yes I do.

See what you mean. So there's a question there then. Who's morphed the most?

Well, the modern tapeworm is a kind of degenerated version of its freely living ancestor. So it's morphed more. But it's not really more developed.

 

[Binkie]

Different type of loop: Can a species evolve back into a previous species. i.e. change a bit and then revert back - over time/conditions? I reckon that would throw the geologists. According to this page they can't. Evolution is boldly stated as a one-way process.

 

[Jonti]

Different type of loop: Can a species evolve back into a previous species. i.e. change a bit and then revert back - over time/conditions? I reckon that would throw the geologists. According to this page they can't. Evolution is boldly stated as a one-way process.

Yes, in that manner it's one way alright. Remember that evolution has to work with what's there already -- there's no evidence of intelligence or forethought guiding the process. (Hence the relevence of the evolutionary kludges, the fact of bad design, I mentioned early on in this thread).

So although something like a bear evolved into modern whales (cetaceans) it doesn't look to be possible for any cetacean to evolve back to the bear-like ancestor. The hind legs in many whale species have been completely lost, you see. Perhaps they could re-evolve from fins, but, no, those new legs are not going to be exactly like the legs the bear-like ancester had.

 

[Jonti]

Just had a thought about Jonti's Herring Gulls and Blackbacks. Can Herring Gulls and Blackbacks interbreed? Or are they separate species? If so, where around the world does the species-change occur?

But, what he said

Yes, I like that one too. Dawkins uses it in his essay 'Gaps in the mind', in order to illustrate why a lawyer who challenged him with the assertion/question that as two species could not interbreed, at what point when one evolved into another, would an offspring be sufficiently different from it's parents to render it incapable of breeding?

An animal species is a reproductive community of populations (reproductively isolated from others) that occupies a specific niche in nature. That's just the best way of describing something we instinctively recognise, an animal species. Turns out it's not to do with the ability to merge genetic material as such.

 

[AnandLeo]

That's OK, don't mention it

It seems you think the phenomena of bad "design" is marginal and trivial (a few out of millions ...). But that is quite wrong. You'll doubtless agree, should you ever need the Heimlich manoeuvre applied to you in the course of a meal.

But of course you're not even trying to be sincere. You are just showing off your skill at being nasty (and hypocritical), right? Why bother? Why not just say "Can you explain the relevance, please?"

I think we should be told!

You are just showing off your skill at being nasty (and hypocritical), right? Why bother? Why not just say "Can you explain the relevance, please?"

Oh yes, indeed!!

 

[AnandLeo]

I wonder if it's possible, for example, that the first single-cell living thing, which all other species evolved from, might still exist relatively unchanged?

Good question. Similarly has the evolution of species stopped or slowed down. A question bothered us from the childhood.

 

[Crispy]

Good question. Similarly has the evolution of species stopped or slowed down. A question bothered us from the childhood.

It's now generally accepted that evolution is not smooth. When there is a sudden change in the environment, then there is a mad rush to inhabit new niches. Examples would include:

Volcanic eruption covers the island in ash. Most plants die, as do all the large animals that live on them. Insects survive and flourish as the plants regrow. You'll get a load of new insect species as the fill niches that were formerly inhabited by other animals.

Mutation in a disease-causing virus wipes out the top predator. Herd populations go unchecked, plants get decimated - new predators move in and adapt to the local environment.

When there are no selection pressures on an organism, it won't evolve much. Some species have evolved very well to their environments, and those environments haven't changed substantially for a long long time. Sharks, for example.

 

[k_s]

But when there is little change in the environment, evolution tends to continue, but in largely pointless directions as directed by sexual selection. Like how humans acquired blond hair.

Its almost surprising sexual selection has had time to make such a noticable impact on humans, considering we evolved reltively recently and have spent the majority of the time since spreading out and colonising more different environments than any other mammal.

 

[AnandLeo]

That's OK, don't mention it

It seems you think the phenomena of bad "design" is marginal and trivial (a few out of millions ...). But that is quite wrong. You'll doubtless agree, should you ever need the Heimlich manoeuvre applied to you in the course of a meal.

But of course you're not even trying to be sincere. You are just showing off your skill at being nasty (and hypocritical), right? Why bother? Why not just say "Can you explain the relevance, please?"

I think we should be told!

Heimlich manoeuvre?
Is that a pre-emptive metaphor?

 

[Jonti]

No, it's a vigourous bear-hug around the chest to expel air from the lungs to dislodge food (whatever) stuck in the airway (wind-pipe) to the lungs.

In adult humans, the wind-pipe comes off from the food-pipe, leading to a risk of choking when eating. The supposition is that this risk is rendered worthwhile, because the same change makes our speech physically possible.

This from http://williamcalvin.com/bk5/bk5ch9.htm
"Compared to other primates, as I noted earlier, our larynx is located low in the neck. It starts out in the higher position but, during the baby's second year, descends several vertebral segments in the neck, elongating the vocal tract. This has some implications for the efficiency of speech: a longer vocal tract enables the larynx's rather crude sounds to be shaped up into the fancy phonemes we use. Vowels, in particular, become better differentiated as the vocal tract lengthens.

"This lengthening brings with it, however, a big disadvantage: our tendency to choke on food or fluids that 'go down the wrong way,' winding up in the lungs rather than the stomach. All other mammals (and human infants less than a year old) have an anatomical arrangement in the throat that generally avoids this -- but apparently the advantages of a lowered larynx have outweighed such common disadvantages as choking on food and aspiration pneumonia."