Human evolution question?

[dlamberth]

If human evolution is still happening (and I can’t imagine why it wouldn’t be), wouldn’t it be very difficult to detect over only a thousand years?

 

[AV1611VET]

If human evolution is still happening (and I can’t imagine why it wouldn’t be), wouldn’t it be very difficult to detect over only a thousand years?

Ask your great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-grandfather.

 

[essentialsaltes]

When we think of evolution as "changes of allele frequency in a population" then I think we have evidence that things like being able to digest milk after infancy has spread, at least in some (sub)populations.

 

[AV1611VET]

If human evolution is still happening (and I can’t imagine why it wouldn’t be), wouldn’t it be very difficult to detect over only a thousand years?

What's the rush?

 

[dlamberth]

If human evolution is still happening (and I can’t imagine why it wouldn’t be), wouldn’t it be very difficult to detect over only a thousand years?

Moving forward in time, I've wondered what evolutionary changes are ahead for Human beings with microplastics so completely in infused into the environment.

 

[AV1611VET]

Moving forward in time, I've wondered what evolutionary changes are ahead for Human beings with microplastics so completely in infused into the environment.

New bodies for those dead to sins, melted plastics for those dead in sins.

 

[sfs]

If human evolution is still happening (and I can’t imagine why it wouldn’t be), wouldn’t it be very difficult to detect over only a thousand years?

In the strictest sense, it's trivial to detect ongoing evolution in humans. Look at recent dramatic population increases in some parts of the world even as populations have started to shrink in other parts.: every allele that has a higher frequency in the former areas than in the latter (and there are lot of them) is currently increasing in frequency in the human population as a whole, which means we're evolving as a species.

Now, if you mean specifically adaptive evolution, I would say that's a lot harder to detect but not impossible, at least in principle. For example, you can look for an association between reproductive success and genotype in large datasets, e.g. the UK Biobank. You will certainly find associations, e.g. alleles associated with higher intelligence or higher educational attainment are negatively correlated with reproductive success. The tricky part is demonstrating causality; in particular, demonstrating that it's not differential success of cryptic subpopulations within the dataset rather than differential success of specific genotypes that is driving the observation.

 

[sjastro]

When we think of evolution as "changes of allele frequency in a population" then I think we have evidence that things like being able to digest milk after infancy has spread, at least in some (sub)populations.

Before the domestication of animals the production of the enzyme lactase typically declined after weaning which led to lactose intolerance in adulthood.
In populations that adopted dairying, individuals who carried a mutation of the regulatory regions near the LCT gene which controls lactase production, particularly the MCM6 gene, could continue producing lactase into adulthood had a nutritional advantage during times of famine or in harsh environments. This advantage led to an increase in the frequency of lactase persistence alleles through natural selection.

The prevalence or lack of lactase production into adulthood amongst various modern populations can be traced back to the environmental pressures faced by their ancestors.

Population/Region	Lactase Persistence (% Adults)	Genetic Mutation	Historical Factors	Environmental Pressures
Northern Europeans	80–95%	-13910*T (in MCM6 gene, upstream of LCT)	Early, long-term dairy farming (Neolithic period)	Low sunlight → milk helped with vitamin D & calcium intake
Southern Europeans	30–70%	-13910*T (lower frequency than North)	Dairying less central than in north	Mediterranean diet diversified protein and calcium sources
East Asians (e.g. Chinese, Japanese)	<10%	Rare or absent	Minimal historic dairy use	No strong selection pressure for milk digestion
Sub-Saharan Africans	Highly variable (10–80%)	Different mutations (e.g., -13915*G)	Some pastoralist groups have dairying traditions	Convergent evolution in pastoralist cultures (e.g., Fulani)
Middle Eastern populations	20–40%	Mixed mutations	Some history of pastoralism	Less intensive dairying historically
Indigenous Australians	<10%	Absent	No traditional dairying	No evolutionary benefit from lactase persistence
Native Americans	<10%	Absent	No dairying before European contact	No selection for milk digestion
Maasai (Kenya/Tanzania)	~80%	African-specific mutations (e.g., -14010*C)	Strong pastoralist tradition, high milk consumption	Milk central to diet; selected for lactase persistence

 

[Tuur]

When we think of evolution as "changes of allele frequency in a population" then I think we have evidence that things like being able to digest milk after infancy has spread, at least in some (sub)populations.

The time-frame though is a thousand years. The adult ability to digest lactose is older. Have seen one source peg it at 20,000 years.

That said, there's something that might be flying under the radar. A tip-off is that even in Northern Europe, digesting lactose beyond infancy isn't 100% of the population, just as the inability to digest lactose in adulthood isn't 100% in places where most of the population can't. What if the ability for adults to digest lactose was already present in the general population but not in high numbers? So let's say consuming milk in desperation, maybe a famine situation,, would of course trigger digestive issues in most, but not in the few who could drink it. If a person were already ill, from hunger or disease from a weakened immune system caused by hunger, that might push them over the edge while those who could somewhat tolerate it and those who could completely tolerate it lived. And how could milk drinking be a desperation move? By not waiting around to process it into cheese or ferment it, and drink it more or less fresh.

"But Tuur, that's evolution," some may say. To which I say it's a classic example of a trait becoming dominate and used in the theory of evolution. But if some have always had the ability to digest milk in adulthood, then it's more of situations favoring an existing trait than an outright mutation. It wouldn't be something that evolved, but something that became prevalent in some populations. IF it was originally rare, as it seems in populations where most adults can't digest milk, it wouldn't even show up in ancient remains with surviving DNA unless a scientist was very lucky.

What if, then, what tends to be called evolution in humans is a matter of a trait that already exists in the general world population, but only moves to the forefront under certain conditions? Will note that during the last pandemic, some seemed to have more resistance to it than others.

For human mutation, we have to look at something like blue eyes, which seems like an either/or kind of thing and not something that randomly shows up worldwide.

 

[essentialsaltes]

The time-frame though is a thousand years. The adult ability to digest lactose is older. Have seen one source peg it at 20,000 years.

Sure, but the question is not about the origin of the original novel mutation (whether once or several times), but the change in frequency of that gene in a population over time.

What if, then, what tends to be called evolution in humans is a matter of a trait that already exists in the general world population, but only moves to the forefront under certain conditions?

That tends to be called evolution because that is evolution, particularly in the sense meant by population geneticists (with which I prefaced my comment).

Evolution is often defined as a change in allele frequencies within a population.

 

[Tuur]

That tends to be called evolution because that is evolution, particularly in the sense meant by population geneticists (with which I prefaced my comment).

It's also rather convenient to give the term a broad umbrella. I suspect it's missing the forest for the trees. How long has homo sapiens been around? 315,000 years? If the ability of adults to drink milk is 20,000 years old, then that's 20/315 = 4/63 of the time homo sapiens has been around. The forest we may be missing is what if human genetics has some wiggle-room, and that's the important trait where survivability is concerned? That would imply that the ability for adults to digest milk could "appear" later if it were "lost" now simply by some maintaining that ability, maybe without their knowledge.

Compare that with blue eyes, a genuine mutation 6,000 to 10,000 years old and not something that crops up here and there.

 

[BCP1928]

If human evolution is still happening (and I can’t imagine why it wouldn’t be), wouldn’t it be very difficult to detect over only a thousand years?

In any case, humans have to a great degree taken control of their selective environment and it wouldn't be naturalistic evolution any more.

 

[essentialsaltes]

It's also rather convenient to give the term a broad umbrella.

If you're a population geneticist, you study the genes of populations. It's not convenient, it's their job, and it's an obvious consequence of evolution. Genes in a species change over time. Boom, that's evolution.

 

[Tuur]

If you're a population geneticist, you study the genes of populations. It's not convenient, it's their job, and it's an obvious consequence of evolution. Genes in a species change over time. Boom, that's evolution.

The problem is practically everything related with biology gets called evolution even when it's a stretch. A survey of genes in a population is a survey of genes in a population, no more, no less, and that can change by factors such as shifts in population or (at the risk of being called a Lamarkian) effects of environment on existing genes. A change in the proportion of existing genes shouldn't properly be called evolution since that's not a change to the genes themselves.

The mutation that caused blue eyes, now that was a change to the genes, a mutation. At one point maybe 6,000 to 10,000 years ago it didn't exist and now it does. It wasn't something floating around in the general population here and there and only really showed up due to a population shift. That is what properly should be called evolution.

 

[Tuur]

In any case, humans have to a great degree taken control of their selective environment and it wouldn't be naturalistic evolution any more.

Why not? How is human manipulation of the environment ultimately different from a beaver building a dam? Manipulation of living conditions is a human trait, and by doing so humans are doing what's natural.

 

[Warden_of_the_Storm]

Why not? How is human manipulation of the environment ultimately different from a beaver building a dam? Manipulation of living conditions is a human trait, and by doing so humans are doing what's natural.

Yeah, apart from the size, scale, scope and materials used in the construction of say the Hoover Dam or the Three Gorges Dam, the latter of which has actually slowed the rotation of the Earth because of the amount of water it holds back, humans do things exactly the same as a beaver.

Do you get why so many things that are artificial are called 'man-made'?

 

[sfs]

That tends to be called evolution because that is evolution, particularly in the sense meant by population geneticists (with which I prefaced my comment).

More specifically, we call it selection on standing variation. In this case, it's unlikely to play a major role in the evolution of lactase persistence, since persistence alleles (at least in the cases I'm familiar with) occur on a single genetic background, which would not happen if an old allele at moderate frequency in the population started to experience positive selection.

 

[sfs]

The problem is practically everything related with biology gets called evolution even when it's a stretch. A survey of genes in a population is a survey of genes in a population, no more, no less, and that can change by factors such as shifts in population or (at the risk of being called a Lamarkian) effects of environment on existing genes. A change in the proportion of existing genes shouldn't properly be called evolution since that's not a change to the genes themselves.

As you note in your next paragraph, we already have a word for changes to genes themselves: it's 'mutation'. We have a different word for all genetic changes to the frequency of different alleles in a population: 'evolution'. Why you think we should start using a different word at this late date is not clear to me.

 

[Tuur]

Do you get why so many things that are artificial are called 'man-made'?

Do you get how all creatures have an impact on their environment? North American megafauna may have led to the distribution of various plants who's range was already contracting by the times the Europeans arrived in force. Beavers have a huge impact. So do prairie dogs; just ask anyone with horses. Sheep and cattle famously don't mix well due to sheep's impact on the environment. Alligators will clear places for themselves that tend to hold water during droughts. Or look at the impact that elephants can have on fauna.

If humans are as much an animal as those named above, then why treat what humans do as a different trait than every other animal on the planet?

If, however, you contend that humans are something apart from animals, as is held by Christian belief, then that is another discussion.

 

[Tuur]

As you note in your next paragraph, we already have a word for changes to genes themselves: it's 'mutation'. We have a different word for all genetic changes to the frequency of different alleles in a population: 'evolution'. Why you think we should start using a different word at this late date is not clear to me.

Because shuffling the distribution of genes in an environment doesn't produce changes like the number of genes a species has. For that you need mutation.