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Female African elephants are evolving without tusks due to ivory poaching

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Re: Female African elephants are evolving without tusks due to ivory poaching

#191

Post by dan_mctree »

jsnell wrote: post #12

In case anyone is wondering about the size of the effect, https://www.nationalgeographic.com/animals/article/wildlife-... has the numbers. Before the war, 2-4% of female elephants were tuskless. Now 32% of newly born ones are. So it's a significant change, but it's not like this property was coming out of nowhere. It started off about as common as humans having green eyes.

Is anyone else surprised at how quick species can seem to evolve in these kinds of ways? Asian and African elephants are supposed to have separated millions of years ago, yet still strongly resemble one another. Yet in a few decades, something as fundamental as the presence of their tusks can shift dramatically. And that in a species with very long gaps between generations.

It makes me suspect there's something else going on here that's not just good old natural selection.

Have they done any tracking to confirm the tuskless elephants are actually being born to tuskless mothers? Or could it be that the parents are actually affecting the way their offspring are born in some lamarckian-esque sense? If there'd be some trick animals can pull to change their offspring in some ways, that ought to be highly effective for long term species survival and should thus be highly selected for.

Re: Female African elephants are evolving without tusks due to ivory poaching

#192

Post by jbay808 »

drtz wrote: post #185
jsnell wrote: post #12

In case anyone is wondering about the size of the effect, https://www.nationalgeographic.com/animals/article/wildlife-... has the numbers. Before the war, 2-4% of female elephants were tuskless. Now 32% of newly born ones are. So it's a significant change, but it's not like this property was coming out of nowhere. It started off about as common as humans having green eyes.

> It started off about as common as humans having green eyes. Elephant poaching has been around since long before the Mozambique civil war. The number of tuskless elephants may have been at 2-4% prior to the war, but that doesn't mean that lower levels of poaching didn't push it up to that level from some much lower naturally-occurring level. 2-4% seems like a _very high_ rate for a trait that could negatively impact…

Further to your point, I read elsewhere that the base rate in captivity is closer to 0.5%.

Re: Female African elephants are evolving without tusks due to ivory poaching

#193

Post by jbay808 »

hanniabu wrote: post #176
rustyminnow wrote: post #77

Earlier quoted context omitted.

Hmm in the context of the article, I'm not so sure it's a good thing. Later on they mention that if this genetic trait gets passed on to males, they die. So along with hunting, males are doubly at risk. It may be advantageous for the survival of an individual to be born without tusks, but it doesn't sound too good for the survival of the species.

Why do they die? Because they can't protect themselves? Or does the trait come with other less desirable side effects for males?

The trait appears to be lethal to males and they do not make it to birth.

It may be the case that at least one typical X chromosome is necessary for survival, and males only get one X chromosome.

Re: Female African elephants are evolving without tusks due to ivory poaching

#194

Post by formercoder »

dan_mctree wrote: post #191
jsnell wrote: post #12

In case anyone is wondering about the size of the effect, https://www.nationalgeographic.com/animals/article/wildlife-... has the numbers. Before the war, 2-4% of female elephants were tuskless. Now 32% of newly born ones are. So it's a significant change, but it's not like this property was coming out of nowhere. It started off about as common as humans having green eyes.

Is anyone else surprised at how quick species can seem to evolve in these kinds of ways? Asian and African elephants are supposed to have separated millions of years ago, yet still strongly resemble one another. Yet in a few decades, something as fundamental as the presence of their tusks can shift dramatically. And that in a species with very long gaps between generations. It makes me suspect there's something else…

Seems like the relative death rates of tusked vs tuskless would matter. Remember the 32% is a percent potentially on a small number. Say to an extreme 99% of tusked elephants were killed, 99% of tuskless were unharmed. If tuskless is a genetic traight, it takes over very quickly even though total population size is smaller.

Re: Female African elephants are evolving without tusks due to ivory poaching

#195

Post by imtringued »

dan_mctree wrote: post #191
jsnell wrote: post #12

In case anyone is wondering about the size of the effect, https://www.nationalgeographic.com/animals/article/wildlife-... has the numbers. Before the war, 2-4% of female elephants were tuskless. Now 32% of newly born ones are. So it's a significant change, but it's not like this property was coming out of nowhere. It started off about as common as humans having green eyes.

Is anyone else surprised at how quick species can seem to evolve in these kinds of ways? Asian and African elephants are supposed to have separated millions of years ago, yet still strongly resemble one another. Yet in a few decades, something as fundamental as the presence of their tusks can shift dramatically. And that in a species with very long gaps between generations. It makes me suspect there's something else…

What do you mean by quick? Evolution is just random mutations. You're basically trying to diversify and spread risk. If there is huge selective pressure only a handful of genes will survive and when they reproduce they will be over represented compared to the previous generation.

Re: Female African elephants are evolving without tusks due to ivory poaching

#196

Post by smk_ »

mulmen wrote: post #148

Is this actually evolution or just selective breeding? By killing elephants with tusks the poachers are favoring elephants with the no-tusk gene. This isn't a lot different than killing a dog that bites sheep, which is how we bred herding dogs. Or a wolf that eats your baby, which is how we domesticated dogs. This trait already existed so it certainly wasn't "engineered due to mass poaching for ivory" as claimed.

Selective breeding is one form of evolution.

Re: Female African elephants are evolving without tusks due to ivory poaching

#197

Post by burnished »

dan_mctree wrote: post #191
jsnell wrote: post #12

In case anyone is wondering about the size of the effect, https://www.nationalgeographic.com/animals/article/wildlife-... has the numbers. Before the war, 2-4% of female elephants were tuskless. Now 32% of newly born ones are. So it's a significant change, but it's not like this property was coming out of nowhere. It started off about as common as humans having green eyes.

Is anyone else surprised at how quick species can seem to evolve in these kinds of ways? Asian and African elephants are supposed to have separated millions of years ago, yet still strongly resemble one another. Yet in a few decades, something as fundamental as the presence of their tusks can shift dramatically. And that in a species with very long gaps between generations. It makes me suspect there's something else…

Nah, looks like natural selection. The article mentions that "The phenomenon of elephants going tuskless is not new. Researchers found the number of tuskless female elephants in Mozambique increased by almost double over 30 years. This overlaps with a period of civil conflict, where armed forces slaughtered 90% of the elephant population to produce ivory.". That is a LOT of selection pressure. Also, the African Elephant Specialist Group (AfESG) [1] published a graph of elephant populations, the reduction in total numbers is pretty dramatic. You might liken this to the way that humans in small, isolated communities will also start to differentiate in a hurry (forex, that one blue family).

[1] https://ourworldindata.org/grapher/african-elephants

Re: Female African elephants are evolving without tusks due to ivory poaching

#198

Post by elwell »

croes wrote: post #23
asdff wrote: post #19

Earlier quoted context omitted.

Its important to realize what this "response" actually is. Nature isn't actively doing anything. You have 100 elephants, maybe 5 are typically born without tusks. Suddenly you kill the other 95 for their tusks, leaving behind those 5 to survive and reproduce and next generation, 33 of your 100 elephants are without tusks or something like that. Over time, humans are acting as a predator in the environment, driving a…

Nature is never doing anything.

This is both true and false.

Re: Female African elephants are evolving without tusks due to ivory poaching

#199

Post by psyfi »

formercoder wrote: post #194
dan_mctree wrote: post #191

Earlier quoted context omitted.

Is anyone else surprised at how quick species can seem to evolve in these kinds of ways? Asian and African elephants are supposed to have separated millions of years ago, yet still strongly resemble one another. Yet in a few decades, something as fundamental as the presence of their tusks can shift dramatically. And that in a species with very long gaps between generations. It makes me suspect there's something else…

Seems like the relative death rates of tusked vs tuskless would matter. Remember the 32% is a percent potentially on a small number. Say to an extreme 99% of tusked elephants were killed, 99% of tuskless were unharmed. If tuskless is a genetic traight, it takes over very quickly even though total population size is smaller.

Exactly that!

I think it is ridiculous to think that more elephant are born without tusks as a kind of "random selection" or even adaption

Re: Female African elephants are evolving without tusks due to ivory poaching

#200

Post by q1w2 »

dan_mctree wrote: post #191
jsnell wrote: post #12

In case anyone is wondering about the size of the effect, https://www.nationalgeographic.com/animals/article/wildlife-... has the numbers. Before the war, 2-4% of female elephants were tuskless. Now 32% of newly born ones are. So it's a significant change, but it's not like this property was coming out of nowhere. It started off about as common as humans having green eyes.

Is anyone else surprised at how quick species can seem to evolve in these kinds of ways? Asian and African elephants are supposed to have separated millions of years ago, yet still strongly resemble one another. Yet in a few decades, something as fundamental as the presence of their tusks can shift dramatically. And that in a species with very long gaps between generations. It makes me suspect there's something else…

A point evolution event can happen extremely rapidly if there's a clearly selective mortality event.

If a new predator is introduced to a population that selectively kills only certain traits, that mutation can become dominant in the population within just one or two generations.

Imagine if aliens came to Earth and killed everyone over 5'6" tall. That "evolution" would be essentially instantaneous.

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