[norcalclimber (OP)]

From what I have always heard, both sharks(some) and crocodiles as well as a few others have not really evolved in the past 65 million years or so.  It seems to me that all the species I have heard of which have not evolved are extremely well suited for their environment.  Does this provide evidence that evolution happens as Jean Baptiste Lamarck suggested, because it is needed, and that if no evolution is needed no evolution occurs?

[Bored chemist]

That's not the normal meaning of Lamarkian evolution.

Some people are red headed, that's not a "needed" bit of evolution, but it happened anyway.
At best, the sharks suggest that evolution is slow in the absence of pressure to evolve.
There's also the point that there are many different sorts of sharks (and crocs), all derived from a common ancestor so the simple answer is  "No".

[norcalclimber (OP)]

That's not the normal meaning of Lamarkian evolution.

Some people are red headed, that's not a "needed" bit of evolution, but it happened anyway.
At best, the sharks suggest that evolution is slow in the absence of pressure to evolve.
There's also the point that there are many different sorts of sharks (and crocs), all derived from a common ancestor so the simple answer is  "No".

While I know there are some sharks(and crocs) which evolved during the past 65 million years, I was under the impression that there are also some which haven't just evolved "slowly", they haven't evolved at all...not even a little.  This seems to suggest not that evolution is slow in the absence of pressure, but rather nonexistent.  Seems to me that implies that evolution is a response to an environmental stressor, and not just the amplification of random traits. 

And 65 million years is not a short period of time when it comes to evolution, since all life you see as well as millions of species which have gone extinct, didn't even really start evolving until ~750 million years ago.

[Bored chemist]

How can we know exactly what the sharks were like 65M years ago?
To support your claim you would need to recover DNA from them and prove that it was exactly the same as today's sharks' DNA.
The best we can say is that evolution is slow when there's no pressure to evolve.
So what?

[echochartruse]

norcalclimber, I know you don't understand my previous posts of the Tasmanian Devil but I believe this is exactly what you are talking about here.

The Devils have genetically altered to mature earlier and to breed eariler due to their cancer which kills them within 3-4 months after getting it. This is the first documented case and supports Jean Baptiste Lamarck. This is adaptation happening as we see it, Now..

Prior to this cancer the gene pool was as clones for the Devil.

[BenV]

That's not the normal meaning of Lamarkian evolution.

Some people are red headed, that's not a "needed" bit of evolution, but it happened anyway.
At best, the sharks suggest that evolution is slow in the absence of pressure to evolve.
There's also the point that there are many different sorts of sharks (and crocs), all derived from a common ancestor so the simple answer is  "No".

While I know there are some sharks(and crocs) which evolved during the past 65 million years, I was under the impression that there are also some which haven't just evolved "slowly", they haven't evolved at all...not even a little.  This seems to suggest not that evolution is slow in the absence of pressure, but rather nonexistent.  Seems to me that implies that evolution is a response to an environmental stressor, and not just the amplification of random traits. 

And 65 million years is not a short period of time when it comes to evolution, since all life you see as well as millions of species which have gone extinct, didn't even really start evolving until ~750 million years ago.

This assumes no pressure on these species - there could well be a selective pressure to not change - they are well adapted to their environment and lifestyle, and deviation from those adaptations might be selected against.

[BenV]

norcalclimber, I know you don't understand my previous posts of the Tasmanian Devil but I believe this is exactly what you are talking about here.

I'm not so sure about that...

The Devils have genetically altered to mature earlier and to breed eariler due to their cancer which kills them within 3-4 months after getting it. This is the first documented case and supports Jean Baptiste Lamarck. This is adaptation happening as we see it, Now..

Prior to this cancer the gene pool was as clones for the Devil.

Well, the disease is leading to lifestyle changes - the devils are breeding earlier as a result of the disease.  There's no need for there to have been any genetic change that leads to younger breeding - the tumour itself will change the ability of adult males to fight for mates.

This, in turn, may well lead to greater genetic variation, as more males are mating (rather than fewer, stronger males monopolising the females).  This isn't Lamarkian - that would involve passing down acquired traits, of which there is no suggestion in the tasmanian devil's case.

In this case an environmental factor (the disease) is leading to population structure changes (earlier mating) which results in a different set of genes being passed on.  Nothing out of the ordinary here. 

In many ways, (and forgive me for speculating) we're seeing something similar in human populations - an environmental factor (medicine) leads to population changes (older couples having children) which change the set of genes that goes into the next generation.

[Bored chemist]

Most cancers are not infectious. The only reason these Devils have this problem is because they have very little genetic diversity. This in turn is because they were nearly wiped out and are now very inbred.
Their current behaviour- mating earlier- is an indirect response to an external stimulus; that stimulus is us.
Nothing to do with Lamarck.

[norcalclimber (OP)]

This assumes no pressure on these species - there could well be a selective pressure to not change - they are well adapted to their environment and lifestyle, and deviation from those adaptations might be selected against.

Ok, that makes sense.  But it was my understanding that Lamarckian evolution basically said that evolution happens because it needs to happen, i.e. giraffes have long necks because they needed them, not by a series of totally random mutations over a few hundred million years.  Under this, it makes sense that a species which is extremely well adapted to it's environment and had no need to change, would be selected against change, which makes sense to be the case here. 

So what am I missing about the situation/science that makes me still feel like it fits a little better with Lamarckian evolution vs Darwinian evolution?

[rosy]

Lamarkian evolution said that an giraffe would stretch its neck during its lifetime and thus its neck would become longer.. the newly lengthened neck would then be passed on to its offspring.

It is like saying that if I have a hand chopped off, and then have a child, the child is likely to be born with no hand.

In the light of modern knowledge, it sounds pretty daft. But Lamark didn't know about chromosomes, let alone genes (tho' he might have been expected to know at least in principle about industrial accidents and amputations).

[norcalclimber (OP)]

Lamarkian evolution said that an giraffe would stretch its neck during its lifetime and thus its neck would become longer.. the newly lengthened neck would then be passed on to its offspring.

It is like saying that if I have a hand chopped off, and then have a child, the child is likely to be born with no hand.

In the light of modern knowledge, it sounds pretty daft. But Lamark didn't know about chromosomes, let alone genes (tho' he might have been expected to know at least in principle about industrial accidents and amputations).

ahhhh, ok, thank you for the clarification.

[Bored chemist]

It may seem odd to consider this idea "It is like saying that if I have a hand chopped off, and then have a child, the child is likely to be born with no hand." but, if Lamarckian evolution worked, Jewish boys would be born with no foreskin.

[norcalclimber (OP)]

It may seem odd to consider this idea "It is like saying that if I have a hand chopped off, and then have a child, the child is likely to be born with no hand." but, if Lamarckian evolution worked, Jewish boys would be born with no foreskin.

Lol, point taken

[echochartruse]

It may seem odd to consider this idea "It is like saying that if I have a hand chopped off, and then have a child, the child is likely to be born with no hand." but, if Lamarckian evolution worked, Jewish boys would be born with no foreskin.

Would that be similar to the French Bulldog and the Pembroke Welsh Corgi which are born with docked tails?

[Bored chemist]

It may seem odd to consider this idea "It is like saying that if I have a hand chopped off, and then have a child, the child is likely to be born with no hand." but, if Lamarckian evolution worked, Jewish boys would be born with no foreskin.

Would that be similar to the French Bulldog and the Pembroke Welsh Corgi which are born with docked tails?

No, not really.

[Geezer]

Would that be similar to the French Bulldog and the Pembroke Welsh Corgi which are born with docked tails?

The Cardigan Welsh Corgi is born with a long tail, but without a cardigan.

[imatfaal]

Would that be similar to the French Bulldog and the Pembroke Welsh Corgi which are born with docked tails?

Tail
Historically, the Pembroke was a breed with a natural bob tail (very short tail). Due to the advent of docking, the trait was not aggressively pursued, with breeders focusing instead on other characteristics and artificially shortening the tail when necessary. Given that some countries are now banning docking, breeders are again attempting to select for dogs with the genes for natural bob tails.

http://en.wikipedia.org/wiki/Pembroke_Welsh_Corgi

they are born with short (not docked) tails - and it seems that more recently they are selectively bred for short(er) tails.  dogs are an unusual case as they are almost entirely selectively bred - we have been choosing (either consciously or unconsciously) for desired traits over many thousands of generations. if you docked a labrador's tail (you should be locked up for starters), the progeny of this dog would not have a noticeably shorter tail.  even if you did this over many generations you would merely select for dogs that were best able to cope with the procedure and whose ability to breed was unaffected - you would not, necessarily, end up with dogs with shorter tails.

lamarck is making a bit of a comeback recently - epigenetics has opened the possibility that not everything that is passable to next generation is received from previous generation (plus random mutation).  together with an appraisal of what lamarck actually said, and a realisation that he shouldnt be bracketed with Lysenko, this has lead to a bit a of a re-reading for Lamarck 

However, what is generally considered to be lamarckism - the inheritability of traits acquired over a single generation - is still not accepted.

[echochartruse]

please read...http://jhered.oxfordjournals.org/cgi/reprint/100/2/236.pdf

C189G gene mutation accommodates the breeding of dogs that require tail docking for showing.
Now tail docking is outlawed.
The dogs with the C189G gene are bred more often for the desired effect for showing.

There are over 17 different dog breeds that carry this short tail gene.

I'm wondering if there has ever been a study done involving Jewish male children who have had their forskin removed to find out whether the forskin is shorter at birth now because of it!

[echochartruse]

However, what is generally considered to be lamarckism - the inheritability of traits acquired over a single generation - is still not accepted.

Excepting wealth, there are other inherited traits we can not deny are passed down in a single generation. That's what makes us who we are. I look like my parents. half of my genes from dad the other half from mum.
Unfortunately gene mutations causes disease which can be also be inherited directly by the next generation.
If both dogs had their tail docked might they both have a gene mutation that caused their offspring to have a short tail? Are you suggesting that t only happens over vast periods of time?
Think about breast cancer, Alzheimer's and many more gene mutations are inherited by the next generation.

[Geezer]

If both dogs had their tail docked might they both have a gene mutation that caused their offspring to have a short tail?

Er well, no.

Dog breeders select a random characteristic of an individual (like, for example, a short tail) and reinforce the desired genetic characteristic by practices that we might consider incestuous in humans. This accelerates the genetic alteration to produce a particular breed in a relatively short time. Unfortunately, the consequent reduction in genetic diversity also reinforces certain undesirable genetic traits, like predispositions to certain abnormalities and susceptibility to particular diseases.