Do you think animals have less genetic variety than humans?

[SiameseSam]

Genetics causes faces to appear the way they do, and it seems to me animals have less distinct looking faces than humans. I dont mean all animals look the same-animals can tell each other apart (animal scientists can also tell individual animals apart), and different animal subspecies (like wolf subspecies for example) all have very distinct looks, but even after watching animal videos on youtube, it seems to me most animals (except for domestic ones like cats and dogs-who were bred for millenia), look alike and dont seem to have as distinct and unique looking faces that individual people have.

[John Cuthber]

Genetics causes faces to appear the way they do, and it seems to me animals have less distinct looking faces than humans. ...

Really?

Also, I think that most people can recognise their pets- even within one breed of animal.

I understand that farmers can recognise individuals among their herds too.

[Robittybob1]

Genetics causes faces to appear the way they do, and it seems to me animals have less distinct looking faces than humans. I dont mean all animals look the same-animals can tell each other apart (animal scientists can also tell individual animals apart), and different animal subspecies (like wolf subspecies for example) all have very distinct looks, but even after watching animal videos on youtube, it seems to me most animals (except for domestic ones like cats and dogs-who were bred for millenia), look alike and dont seem to have as distinct and unique looking faces that individual people have.

Without a doubt in farmed animals where there is limited number of males (rams mate over 100 ewes and bulls are mated across hundred of thousands of cows with the artificial insemination programs).

This limits genetic variation and is what is sought after by the farmers , with the best genetics being bred year after year.

Edited January 5, 2015 by Robittybob1

[Strange]

Genetics causes faces to appear the way they do, and it seems to me animals have less distinct looking faces than humans.

 

Genetics and other factors.

 

That might mean that there are more genes involved in the definition of the human face (structure and musculature) than some other animals (although other primates are obviously close to humans in this respect). But even if true (which I doubt) it says nothing at all about genetic diversity in general.

[Yoseph]

From what I've heard we have actually evolved to notice the differences between each other more acutely than those of animals as a means of determining friend or foe and building a social structure. I vaguely remember seeing an experiment in a documentary that suggests that babies recognise the differene between animals just as well as between humans. I also remember hearing this, and have thankfully found evidence that I didn't just imagine it on wikipedia:

 

"There is about 2–3 times more genetic diversity within the wild chimpanzee population on a single hillside in Gombe, than in the entire human gene pool.[121][122][123][124]"

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

[imatfaal]

Thanks Yoseph - I knew I had read something on those lines but couldn't find it.

 

Perhaps someone can help fill my other memory-flaw on this subject - I read an article on the artificial-intelligence vs human-intelligence methodology of recognizing faces; it concentrated on the actually very difficult task and how amazingly optimised we have become at that seemingly simple everyday occurrence.

[SiameseSam]

 

Genetics and other factors.

 

That might mean that there are more genes involved in the definition of the human face (structure and musculature) than some other animals (although other primates are obviously close to humans in this respect). But even if true (which I doubt) it says nothing at all about genetic diversity in general.

What other factors besides genetics? Bone and skin structure is influenced by genetics-so I'd say genetics is really the only main factor that causes faces to look the way they do.

[cladking]

It is near extinctions that cause evolution and genetic differences. Humans are much more capable of changing their habitat by relocating than any other animal so humans will have much less genetic difference than other animals. Their ability to relocate is their adapability as well as the ability to adapt habitat to their own needs. "Near extinction" is a very very gradual process unless populations are reduced to extremely low numbers. Individual variation is a function of change which is driven by near extinctions.

[Strange]

What other factors besides genetics?

 

Environment. In the womb and later development. Even identical twins don't always look identical.

It is near extinctions that cause evolution and genetic differences.

 

No it isn't. That is a very exceptional case.

[Delta1212]

Humans have evolved to have and to recognize distinct faces as a means of identification. It's entirely possible that a larger share of our genetic diversity goes into facial structure than for most animals.

 

Humans overall, though, are among the least genetically diverse animals on the planet having gone through a relatively recent (on geological and evolutionary time scales) population bottleneck.

[Robittybob1]

Humans have evolved to have and to recognize distinct faces as a means of identification. It's entirely possible that a larger share of our genetic diversity goes into facial structure than for most animals.

 

Humans overall, though, are among the least genetically diverse animals on the planet having gone through a relatively recent (on geological and evolutionary time scales) population bottleneck.

That is very interesting. Has this been shown in genetic tests?

[cladking]

 

 

 

No it isn't. That is a very exceptional case.

 

Where did you get such an idea and how does it explain the relative lack of variability in humans and the fact that change in species, according to the fossil record, are sudden? How does it explain the overlap of extensive DNA between oak trees and humans. The entire theory of evolution needs to be revisited in light of further evidence. You can bury me in links or deflect the questions by name calling and claiming it's off topic but I seriously doubt you can address them.

[SiameseSam]

Humans have evolved to have and to recognize distinct faces as a means of identification. It's entirely possible that a larger share of our genetic diversity goes into facial structure than for most animals.

 

Humans overall, though, are among the least genetically diverse animals on the planet having gone through a relatively recent (on geological and evolutionary time scales) population bottleneck.

I recently had a conversation with a friend about this topic, and he said he thinks animals have just as much different faces as humans do, but people dont see it that way because they dont see them often-for the same reason people say certain ethnic groups look alike. Do you agree or disagree?

[Phi for All]

I recently had a conversation with a friend about this topic, and he said he thinks animals have just as much different faces as humans do, but people dont see it that way because they dont see them often-for the same reason people say certain ethnic groups look alike. Do you agree or disagree?

 

I think this is closer to reality. It's interesting that we put a lot of importance on skin color, hair, and facial markings, but we tend to ignore them when it's an animal covered in fur.

 

If an animal makes sounds like humans do, this can also help to identify individuals. I have friends who look rather like a lot of folks do, but they have a distinctive laugh or tone of voice that makes them unique.

[Delta1212]

I recently had a conversation with a friend about this topic, and he said he thinks animals have just as much different faces as humans do, but people dont see it that way because they dont see them often-for the same reason people say certain ethnic groups look alike. Do you agree or disagree?

I think animals have ways of distinguishing individuals, but they are dependent upon species. Humans aren't the only ones that use faces as one manner of identification, but that's very far from the only strategy employed in the animal kingdom, and humans do actually have better than average vision during the day (and are comparatively weaker in e.g. our sense of smell) so for us a visual means of distinguishing individuals makes sense. Smell, sound and touch are all equally valid, and even for animals that identify individuals by sight, it doesn't necessarily have to be localized to to facial features.

 

So if I had to guess (because I don't remember what articles I've read on the subject well enough to find them) I'd say humans are particularly well adapted to recognizing faces (though not necessarily uniquely adapted for it) and that our facial features have probably at least someone adapted to make this easier to do, since there is an obvious social payoff in being easily recognizable when people are more likely to mistrust strangers.

[Arete]

It is near extinctions that cause evolution and genetic differences. Humans are much more capable of changing their habitat by relocating than any other animal so humans will have much less genetic difference than other animals. Their ability to relocate is their adapability as well as the ability to adapt habitat to their own needs. "Near extinction" is a very very gradual process unless populations are reduced to extremely low numbers. Individual variation is a function of change which is driven by near extinctions.

 

 

This post is entirely wrong.

 

1) "Near extinctions" do not cause evolution and genetic differentiation. Mutation, selection and drift do. www.sciencemag.org/content/318/5858/1842.full

2) Humans do not have less genetic variation than other animals. We have considerably more than many.

3) Dispersal capability and behavioral adaptation do not reduce genetic diversity.

4) "Near extinction" otherwise known as a population bottleneck is generally not a gradual process.

5) Population bottlenecks reduce genetic diversity.

6) I think you meant population variation, which is positively correlated with effective population size. Large populations are diverse, with generally more rapid rates of evolution than smaller populations.

[Delta1212]

 

 

This post is entirely wrong.

 

1) "Near extinctions" do not cause evolution and genetic differentiation. Mutation, selection and drift do. www.sciencemag.org/content/318/5858/1842.full

2) Humans do not have less genetic variation than other animals. We have considerably more than many.

3) Dispersal capability and behavioral adaptation do not reduce genetic diversity.

4) "Near extinction" otherwise known as a population bottleneck is generally not a gradual process.

5) Population bottlenecks reduce genetic diversity.

6) I think you meant population variation, which is positively correlated with effective population size. Large populations are diverse, with generally more rapid rates of evolution than smaller populations.

We do actually have fairly low genetic variation compared to other animals, just not any other animal, and not for the reasons he seems to be claiming.

[cladking]

1) "Near extinctions" do not cause evolution and genetic differentiation. Mutation, selection and drift

do. www.sciencemag.org/content/318/5858/1842.full

 

 

Why wouldn't they?

 

When waters rise only the swimmers survive. Their off spring are preselected for the ability to swim. No matter what event or change occurs in a biological niche some individuals have a superior chance of survival and others do not. It usually won't have have anything to do with whether or not the individual is fit or fast. It has to do with the ability to survive and/ or adapt (individually) to the change. All life is individual but occurs in the context of species. A rabbit is a rabbit and even the fittest rabbit will make a good meal for a cheetah.

 

2) Humans do not have less genetic variation than other animals. We have considerably more than many.

 

 

I'm sure there are many animals with less variation than humans but this is due to their nature and relative lack of near extinction events or other forces that drive evolution (none of which is survival of the fittest). Even local populations suffer "population bottlenecks" and then the survivors breed with individuals which didn't suffer that bottleneck. If all members of a spcies are local then the lack of bottlenecks translates to less individual variation and a threat to the species by new changes or disease.

 

3) Dispersal capability and behavioral adaptation do not reduce genetic diversity.

 

 

Individuals which are able to leave a changing habitat have a much higher probability of surviving than those who don't. If you left Paris before the plague you improved your odds of survival.

 

4) "Near extinction" otherwise known as a population bottleneck is generally not a gradual process.

 

 

Actually it is. It is always ongoing even as populations increase because individuals vary and all life is individual. Even as a new threat kills some members, population can increase and the species is changing. Of course it is extremely gradual except when populations are significantly reduced.

 

5) Population bottlenecks reduce genetic diversity.

 

 

 

This should not be true. All survivors are still the members of the same species and most habitat changes will simply select individuals with a specific trait within that species. Obviously I'd agree that some extinction events can greatly reduce genetic diversity but this would not be the norm and never the norm so long as the event is local.

 

6) I think you meant population variation, which is positively correlated with effective population size. Large populations are diverse, with generally more rapid rates of evolution than smaller populations.

 

 

There are other things that drive change in species. We can see the changes when there are large populations because there are more fossils. We don't see the "missing links" because there are few survivors.

 

 

 

 

 

 

 

Humans and probably termites invented agriculture through a sort of artificial series of extinction events. Individuals which lacked the desired traits were simply excluded from reproducing. Individuals with undesirable traits were effectively subject to extinction.

 

In nature this same process happens at the whim of what we call "chance" and it is driven by habitat change and near extinctions. If toad populations drop then racoon populations plummet with the survivors being individuals with the knowlege and experience required to find other food. These individuals are already distinct by nature such as, perhaps, a relative dislike for the taste of toads. Species naturally adapt to a wider array of foods, behaviors, and conditions. The individuals which survive are genetically different than those which don't and their off spring suddely manifest this difference since they get their genes from both parents.

 

...There are no missing links.

Edited January 6, 2015 by cladking

[Arete]

Why wouldn't they?

 

Population bottlenecks reduce effective population size, and thus genetic diversity. A reduction in genetic diversity generally results in slower rates of evolution within a population. This is really basic population genetics.

http://evolution.berkeley.edu/evosite/evo101/IIID3Bottlenecks.shtml

 

 

I'm sure there are many animals with less variation than humans but this is due to their nature and relative lack of near extinction events or other forces that drive evolution (none of which is survival of the fittest).

 

 

Actually the exact opposite is true. Most of the species which have depauperate genetic diversity compared to humans have recently been through a population bottleneck. E.g. cheetahs, elephant seals, american bison, etc. In fact, humans are thought to have gone through a population bottleneck around 140 -200,000 years ago. http://en.wikipedia.org/wiki/Mitochondrial_Eve

 

 

Individuals which are able to leave a changing habitat have a much higher probability of surviving than those who don't. If you left Paris before the plague you improved your odds of survival.

 

Strong selective pressure reduces genetic population diversity - it does not increase it. Again this extremely fundamental population genetics. http://agron-www.agron.iastate.edu/~weeds/AG517/Content/WeedEvol/NaturalSelection/genediverse.html

 

 

Actually it is. It is always ongoing even as populations increase because individuals vary and all life is individual. Even as a new threat kills some members, population can increase and the species is changing. Of course it is extremely gradual except when populations are significantly reduced.

 

No, it isn't. A population bottleneck is a sharp reduction in effective population size. Therefore, by definition, rapid. Population reduction is also not an ongoing process. http://en.wikipedia.org/wiki/Population_bottleneck

 

 

This should not be true. All survivors are still the members of the same species and most habitat changes will simply select individuals with a specific trait within that species.

 

I have no idea why you would think that a reduction in effective population size would lead to an increase in genetic diversity. It is not the case, and I can't see any logical reason why you would expect it be so.

 

 

Obviously I'd agree that some extinction events can greatly reduce genetic diversity but this would not be the norm and never the norm so long as the event is local.

 

It is almost universally observed that a population that is at risk of extinction displays low genetic diversity. http://en.wikipedia.org/wiki/Conservation_genetics

 

 

There are other things that drive change in species. We can see the changes when there are large populations because there are more fossils. We don't see the "missing links" because there are few survivors.

 

 

I'm not talking about the fossil record, I'm talking about a well characterized relationship between effective population size and genetic diversityhttp://www.nyu.edu/pages/projects/fitch/courses/evolution/html/genetic_drift.html.

 

Effective population size and genetic diversity are positively correlated. It really is that simple.

[cladking]

 

Population bottlenecks reduce effective population size, and thus genetic diversity. A reduction in genetic diversity generally results in slower rates of evolution within a population. This is really basic population genetics.

http://evolution.berkeley.edu/evosite/evo101/IIID3Bottlenecks.shtml

 

 

Effective population size and genetic diversity are positively correlated. It really is that simple.

 

Perhaps I'm misunderstang something here but I believe the author is looking at the logic wrong. "Species" don't have any genes at all, far less variety. Only individuals have genes and all the variety exists between individuals. Certainly some bottlenecks will necessarily affect indiduals that don't have specific genes and hence reduce diversity but I believe most of these bottlenecks are not selective of things so gross as genes. They will tend to affect behavior, or knowledge, or things that can't be quantified like chance or the ability to detect unknown dangers. Extinction drivers can be virtually anything and are often unidentifiable even in real time. Minor changes in habitat can have sudden and devastating effects on species. If you periodically flood a roomfull of flies with intense infrared or microwave radiation that kills those oin direct line with the source then the only survivors will be those on the undersides of objects or in the shade. These individuals will tend to have as much diversity as the population as a whole did but they will be fundamentally different and their off spring can be virtually a different species. If the off spring reintegrate with normal flies the resultant will be increased variability.

 

You can actually see this process at work with species that have short life spans. The speed of change is dependent on whether the extinction factor affects every individual or only those that have specific characteristics. If only the fast flies, survive or those with the briefest time to become airbourne, or the most energetic then you will see something like "survival of the fittest". I seriously doubt that many bottleneck causes are of this nature. An area doesn't suddenly become overrun with cheetahs so only the fastest rabbits survive. Rather the stresses are often specific and usually more widespread and robust. Being "fit" or even "smart" simply won't save many individuals except in specific instances and so long as the stresses remain his genes and life remain in danger. Every animal seeks to survive and when most die it's because their genes simply aren't up to the new task as defined by mother nature. Hence mother nature herself is selecting new specimens for a new sprecies that can survive. Mother nature doesn't select for genes or the survivors would tend to be random from the population rather than sharing one or combination of specific traits that allowed them survival.

 

 

I have no idea why you would think that a reduction in effective population size would lead to an increase in genetic diversity. It is not the case, and I can't see any logical reason why you would expect it be so.

 

 

 

Certainly a significant decrease in population might severely reduce diversity in that locality. But, if the forces that reduce population were wholly random (it never is), then individuals will still be as diverse as they were before the decline. There will be fewer so scarcer genes might disappear but there will still be "one of each type" as it were.

 

 

The forces causing the decline aren't random and don't affect each individual the same. Traits will serve to protect or destroy some individuals. These individuals will usually be nearly as diverse but, more importantly, whatever trait saved them will tend to breed true no matter how subtlely it is expressed. The new population won't be more diverse, they will be different. When this "new species" interbreeds with populations that were not subjected to the stress their offspring will have increased diversity and a better chance of surviving the same or similar insult. "Survival of the fittest" simply doesn't apply. Individuals which are fit may have no better chance of survival than those which prefer to nap in the early afternoon or prefer fish to fowl. Strenght, speed, intelligence, fine eyesight etc are of value to the individual in mate selection and chances of survival under normal conditions but in most bottlenecks this is going to be less true. Bottlenecks can result from a single source or a multitude and they'll affect each member of a species individually.

Edited January 7, 2015 by cladking

[Endy0816]

Random events may not have an even distribution in their effect.

 

ie. 5 random numbers 1-10(Random.org)

 

3 8 4 9 3

 

Due to sheer luck some numbers were lost and one number came up twice. Were three to represent a person with bluish skin then many of the next generation's population will end up looking like this guy:

 

 

 

Anyways back to OP's question, this should give a good overview:

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

 

Basically involves how you are wired and what your brain subsequently trains at from birth onwards. Personally I would say I've always been able to recognize my own pets even at a distance after having them for awhile. I'm sure other animals could be individually identified were you exposed to them often enough.

 

Edited January 7, 2015 by Endy0816

[Arete]

These individuals will tend to have as much diversity as the population as a whole

 

This is your misunderstanding - they don't. A population which undergoes a rapid reduction in effective population size loses a considerable degree of genetic diversity. Rare alleles are more likely to be lost than common alleles. Even when the population recovers, genetic diversity is lower than a population which has remained stable over the same duration.

 

It's been explained in the previously linked articles, but this picture explains it succinctly:

 

[cladking]

 

This is your misunderstanding - they don't. A population which undergoes a rapid reduction in effective population size loses a considerable degree of genetic diversity. Rare alleles are more likely to be lost than common alleles. Even when the population recovers, genetic diversity is lower than a population which has remained stable over the same duration.

 

It's been explained in the previously linked articles, but this picture explains it succinctly:

 

 

 

 

Perhaps I'm not stating my contention clearly. I'm saying that each individual in genetically diverse and not only does each individual carry the genes which represent himself and his species but many more that aren't expressed. Of course much of this coding is common to all individuals and of course when there are fewer individuals rare genes might and will disappear.

 

I'm suggesting that diversity, both individual and species, is usually irrelevant to the ability of an individual to survive. It is only through survival the individual can affect the gene pool. And at the same time the probability of the individual to survive is usually based on behaviors and the specific genes that lead to these behaviors rather than the degree to which "he" is fit. Among the survivors you'll see fitness sometimes played a role but typically it will appear to be primarily luck of the draw.

 

It's in the off spring of the survivors where you see the changes. You say that even random numbers show a severe crippling diversity but I don't believe this because every individual has countless millions of genes. Many of these genes are simply irrelevant to the ability of an individual to survive almost any bottleneck. Green eyes might matter to individual humans even in such critical areas as mate selection but how many extinction events have given prefential treatment to green eyes? Survivors will make do with brown eyed or blues eyed mates anyway.

 

But these survivors which are just as diverse as any other members of their species get selected based on any of the craziest parameters thrown at them by mother nature. It can simply be anything at all from geography, elevation, handedness, or foot size. It might seem that genes play no role in whether a certain individual is saved by being under the surface of the water but in fact even though it's an individual with free will, some individuals are far more likely to be diving than others and this can be related directly or indirectly to the individual genes. Indeed, it will be directly or indirectly related and these individuals which have the same diversity as other members of their species will breed true. Whatever gene directly or indirectly led them to be under the water will express itself in their offspring and the local species will have changed.

 

Increased diversity doesn't arise until these, normally very similar, off spring interbreed with others of the species that didn't undergo the extinction. This is evolution. It is driven by population "change" and diversity is created at a later time by this same change.

 

Just as it has been said "all politics is locaL", the same is true of evolution. Evolution simply doesn't occur to species, it occurs to individuals and it occurs suddenly. "Extinction" is an ongoing process because individuals grow old and die or are eaten. Local regions have populations that increase or decrease at least by one with every birth and every death. Very few of these population changes are important to evolution unless there is a mutation that is beneficial to an individual. These will change the species iff they breed true. Slower rabbits have a higher chance of being eaten but "unlucky" rabbits have the highest chance. If you examine the detail of this "bad luck" you'll see a glacial extinction event that is driving change even while the real driver of change, polulation decrease, isn't at work. Even after countless millions of years a rabbit still can't ourrun a cheetah so "survival of the fittest" is hardly the answer while the reality is at hand and unseen.

Edited January 7, 2015 by cladking

[Arete]

You say that even random numbers show a severe crippling diversity but I don't believe this because every individual has countless millions of genes.

 

Actually, the human genome contains approximately 20,000 coding genes. http://en.wikipedia.org/wiki/Human_genome#Coding_sequences_.28protein-coding_genes.29

As a diploid organism, each human carries a maximum of 2 copies of each orthologous gene. Allelic variation (i.e. variation in the coding sequence of the same gene) therefore occurs predominately between individuals within a population.

 

It therefore stands to reason (and is backed up by extensive empirical observation) that reductions in population size reduce genetic variation in a population.

 

Just as it has been said "all politics is locaL", the same is true of evolution. Evolution simply doesn't occur to species, it occurs to individuals and it occurs suddenly.

I'm sorry but this is quite simply incorrect. Evolution is a population process - defined as change in allelic frequency over time. This is super introductory biology. As the genetics of an individual does not change over the course of its lifetime, they categorically cannot evolve, in a biological sense.

Species are generally defined as meta-populations of organisms with a shared evolutionary trajectory. I'm not sure how you could think or justify saying that "Evolution simply doesn't occur to species".

Edited January 7, 2015 by Arete

[cladking]

I believe you are confusing a process to learn about "rabbits" with rabbits themselves and then illegitimately extrapolating the knowledge gained to apply to all life.

 

In reality there is no such thing as "a rabbit". There aren't ten rabbits in the entire world because each rabbit is different. You can slice and dice one of them for dinner or study but it will still be an individual (even in stew). Even in symbiotic relationships all life is individual and each individual is different. Since there's no such thing as "a rabbit" it is impossible to dissect them or to study them except through observation and established theory; rabbits are mammals, for example. Most of them hop.

 

It is here, in observation, that current hypotheses are seen as being highly questionable. From the perspective of lab and the concept that "a rabbit" exists many extrapolations are possible and obvious. If rabbit populations decrease then obviously some genes are likely or certain to become extinct. This obviously is decreased diversity by defnition. But the fact remains that there is no such thing as "a rabbit" and that each rabbit in the world has its own distinct genes. Every individual is already diverse enough for its own needs or it will soon die whether its otherwise fit or not.

 

There simply is no such thing as an "average rabbit". There are norms and parameters of construction and behavior but there is no individual that is representative of "a rabbit". If "a rabbit" actually existed we could somday create the prototypical rabbit and then predict its every behavior. Obviously we will never be able to predict behavior except in the grossest sense (rabbiyts taste better with onionms). This means there's also no such thing as "rabbit populations". This is simply a short hand method we use to communicate the concept that the total number of individual rabbits always fluctuates. These are terms we use to fascilitate communication and to better develop and understand the processes used to understand nature: they simply are not representative of nature (rabbit) itself. It's this disconnect between reality and our study of it that results in observation being contrary to "theory". We extrapolate our understanding of chemistry, physics, zoology etc to apply to something that doesn't even exist except as a model for communication and understanding.

 

The reality is that we can see how things like "natural selection" or breeding simply trumps survival of the fittest. We can see that there are numerous "missing links" caused by the lack of not rabbits but rather the individual proto rabbits. All life is individual just as all fossils and the lack of fossil record simply "proves" that individual was among a group that was very much less numerous than its ancestors and that it is much different that its ancestors because this is the very way nature imposes diversity; by first removing it among groups of individuals largely by means of eradicating much less than simply random genes (among individuals).

 

I'm sure your expertise here exceeds mine by a wide margin but this is irrelevant because my visceral knowldge and my experience with evolution among short lived species combined with logic might be more reflective of the reality than a means to study reality that might be applied illegitimately; biology/ evotutionary theory/ etc.

 

Basic science says theory must fit observation. There must be a reason for the disconnect between theory and observation and this post is my hypothesis for the existence of this disconnect.