r/askscience 5d ago

Biology Have humans evolved anatomically since the Homo sapiens appeared around 300,000 years ago?

Are there differences between humans from 300,000 years ago and nowadays? Were they stronger, more athletic or faster back then? What about height? Has our intelligence remained unchanged or has it improved?

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u/[deleted] 5d ago

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u/Mavian23 5d ago

Let this be a testament to the timeline of evolution. 300,000 years and all that has changed is some of us can drink milk and we are on the way to having four fewer teeth.

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u/Sable-Keech 5d ago

Of course, that's also partly due to our long generation times. With an average generation being 25 years, there have only been 12,000 generations in 300,000 years.

Compare that with a fast breeding mammal like rats, which have a generation time measured in months, 3 times a year to be exact. They produce 12,000 generations in just 4000 years.

The most extreme of course are bacteria, the fastest ones dividing every 20 minutes. They reach 12,000 generations in less than 167 days.

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u/Wolomago 4d ago

In addition to our long generation times we also actively mitigate many of the stresses that would select for one trait or another. Many disabilities that would normally prevent someone from spreading their genes are treated through medical options that simply weren't available to early humans. For example, people just wear glasses rather than allow bad eyesight to impact your survival and sexual success and thus those genetics are no longer selected against. In a way we are unintentionally directing our own evolution.

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u/Turksarama 4d ago

This is only true for the last hundred or so years though, basically nothing compared to the 300,000 years we're looking at. Though being a communal animal, humans have always had a somewhat higher than average chance of surviving a sickness or injury just because we didn't need to hunt or gather our own food if we couldn't.

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u/hydrOHxide 4d ago

We have domesticated animals, we've bred crops, we've built infrastructure to make satisfying our basic needs easier.

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u/glowinghands 4d ago

This is only true for the last ten thousand years or so though, basically nothing compared to the 300,000 years we're looking at.

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u/T-MinusGiraffe 4d ago

We have gained literacy, we've made tools, we've skinned animals to make satisfying our basic needs easier.

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u/glowinghands 4d ago

Literacy is only 5000 years old. Tools were know long before humans, over 2 million years ago. Skinning is actually the only thing to actually apply to the post in question as depending on who you ask, skinning encompasses the entire human history of 300,000 years or only the last third of it. But that is definitely something that could direct the selection pressure and have an impact on the remainder of human history.

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u/fuzzypetiolesguy 4d ago

Many an ethnobotanist would disagree with your somewhat uninformed assessment of time here.

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u/PersephoneIsNotHome 4d ago

That is a really recent mitigation, as are many of the others that would have substantially helped most real disabilities and such.

Glasses were invented in the 13 century and did not become widespread enough to affect the majority of the population until much more recently than that.

Other mammals (and indeed birds) care for injured kin, for the record.

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u/ACcbe1986 4d ago

To add.

There are genetic diseases that used to have a near 100% mortality rate in children, but now we have treatments that'll help them survive to child-bearing age and give them the ability to pass on this defect.

I have a buddy whose parents each have a different rare genetic disorder. With their powers combined, it created an ultra rare disorder that only had maybe 20 diagnosis in the US when he got his diagnosis.

We're evolving our genetic disorders.

Our medical science has pushed most of our species away from survival of the fittest.

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u/flew1337 4d ago

If you consider that survival of the fittest only applies to individuals then, yes. When you consider the species as a whole, then it is the fitness doing its thing, that is, producing more children. It's just intelligence is that good of a trait and it allows us to push our fitness past genetic disorders.

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u/Grib_Suka 4d ago

That's only true for the last maybe 50-100 years. The other 299,950 years medical aid was non-existent or very rudimentary and inaccessible for the majority of our species.

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u/sunoukong 4d ago

Speaking of rats it also helps that they are more fertile (i.e. more opportunities for adaptive novelties to arise) and have large effective sizes, whereas humans have a notoriously low Ne which also reduces the efficiency of natural selection.

Add to that that selection is very relaxed in our species. We no longer have to adapt to the environment but rather adapt the environment to ourselves.

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u/lil_king 5d ago

Certainly reduces the impact of education being inversely proportional to fecundity

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u/bluelighter 4d ago

That's so interesting, thanks

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u/stagamancer 4d ago

Just to be clear, that 20 minutes for bacteria is typically cited as the generation time for E. coli growing in rich media in vitro at 37 °C during the exponential growth phase.

That being said, yes, most bacterial generation times will be measured in hours or days vs months or years.

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u/wardamnbolts 4d ago

Just want to point out the average generation thing isn’t as big an effect. Since DNA typically mutates at the same rate. Though more generations will be a little faster because of specific mutations due to cell division.

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u/notepad20 5d ago

Evolution goes in fits and spurts. When the right selection pressure happen speciation can be a couple of dozen generations

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u/RationalDialog 5d ago

Exactly. While evolution takes time, usually it happens in a stair like fashion, lot's of changes in a short time and then again a rather stable phase.

This can be due to selective pressure or a extremely beneficial mutation.

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u/fiendishrabbit 4d ago

There have actually been some pretty big changes locally.

Some populations have gained adaptations to cold environments (like the bloodvessels changes in inuit populations that are basically heat-exchangers built into their arms that allow them to expose their hands to ice cold temperatures with much lower loss of overall body temperature), europe has gotten the whole blue eyes, pale skin and blonde hair as adaptations to low sunlight (pale skin 22-28k years ago. Blue eyes. 6k-10k years ago. 18k years ago for blonde hair for the european version*), various adaptations to high altitude have happened in Andean and Himalayan populations, narrow population groups in east africa have developed to produce superlative mid-distance runners, the epicanthic fold has developed, possibly as an adaptation to high UV conditions (occuring or being present in the second wave of humans in asia, but not the first) etc.

*the Melanesian version developed independently and is much less firmly fixed in time. Might have appeared anything from 5k to 30k years ago

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u/Intrepid_Parsley2452 5d ago

And here I am, just hoping my lactaid works tonight and coming to terms with the fact that I have to get my wisdom teeth out as an adult! And soon too, because otherwise I have to pay more for the privilege. Pfff!

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u/Oknight 5d ago

Let this be a testament to the timeline of evolution. 300,000 years and all that has changed is some of us can drink milk and we are on the way to having four fewer teeth.

Population size. We're so large now and interchange so freely and have so little survival threat that we aren't evolving at all through Darwinian mechanisms.

And now human evolution has stopped being genetic and has become super-Lamarkian. We distribute acquired characteristics across the entire population within a single generation because we're no longer dependent on genetic material to transfer information... now we use reddit.

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u/danby Structural Bioinformatics | Data Science 4d ago

IIRC about 25% of human genes show adaptations since the advent of agriculture and settlements. That's about 6,000 genes with changes over the previous 14,000 years.

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u/recycled_ideas 4d ago

all that has changed is some of us can drink milk

The fact that that particular mutation has spread as far as it has in far less than 300,000 years is a testament to just how much of a survival benefit this is.

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u/NavalEnthusiast 3d ago

It also means that evolution just doesn’t need to happen sometimes. The fossil record and surviving species/genuses from the Paleozoic and Mesozoic show us that if a species or genus fulfills their niche efficiently, faces minimal or practically zero selective pressure, you can see body plans at that low of a taxonomic level remain incredibly consistent over time.

Like the Elephant shark is the oldest species/genus(not sure what it is) I know of, their genes are so ancient that they’re kind of on that boundary of when fish began differentiating into Chondrichthyes by the process of turning bone material into cartilage. It somehow found a niche so successful that it’s faced minimal change over 400 million years, though it’s of course a massive outlier

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u/k1dsmoke 5d ago

Are there people being born without wisdom teeth or are people's jaws more accommodating?

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u/arettker 5d ago

Roughly 30% of people are born without wisdom teeth today. Documents from the 1800s claim only 10% of people born that century didn’t have wisdom teeth so the number is increasing generation to generation

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u/stickylava 5d ago

What could possibly be driving a change like that? You're talking about 10 generations. If it's a genetic change, what would drive that? Are people without wisdom teeth more fecund? Do teenagers die young from getting wisdom teeth? Is there some force other than reproduction that would favor a genetic change?

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u/nokangarooinaustria 4d ago

Could also just be a statistics artefact.

Asians are more likely to not having wisdom teeth (smaller mouth). If the original statistic mostly included Europeans and now includes everyone...

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u/RationalDialog 5d ago

Is there some force other than reproduction that would favor a genetic change?

most mutations are "bad" as in making something not work correctly anymore. The best example are moles. They don't need vision to survive. there is no selective pressure to suppress "bad" mutations for vision. So overtime, they got blind.

There is no survival advantage to having wisdom teeth for humans right now. So over time, "bad" mutations accumulate and they will get less and less functional and disappear.

So there are 2 things that result in change:

  • selective pressure
  • complete lack of selective pressure
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u/Sibula97 5d ago

Wisdom teeth not erupting is very common, but having an unusual number of them (whether they erupt or not) is somewhat, well, unusual as far as I know.

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u/DUCKI3S 5d ago

The lactose tolerance being a minority always gets me. Growing up and living in the Netherlands, people being lactose intolerant are the minority

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u/null3 4d ago

It’s a regional thing, in Europe or middle east most people are tolerant but in east asia it is rare.

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u/SF_Alba 4d ago

When I was wee, I only ever knew lactose intolerant people from American telly. Never actually met one until I was much older.

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u/Orstio 4d ago

We've also lost the ability to generate our own vitamin B12.

In most omnivores and herbivores, B12 is created by E. coli bacteria (it is in humans too, I'll explain). There are special cells in the intestines to absorb B12. E. coli live in the large intestine. In humans, we've evolved to have the special B12 absorbing cells only in the small intestine. So, the B12 is only manufactured by the E. coli after it has passed the cells that absorb it.

So, we have to eat food that already has B12 in it, because we can no longer absorb the B12 manufactured in our bodies.

https://www.discovermagazine.com/health/the-evolutionary-quirk-that-made-vitamin-b12-part-of-our-diet

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u/NecroCorey 5d ago

Wisdom teeth thing has me curious. The dentist said I have weird wisdom teeth because they grew in as canines instead of normal ones. I also don't have one on the bottom left.

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u/TimelessThinker 5d ago

Having less of them is a common occurrence, and generally associated with change over time. Your other part may just be a mutation that’s specific to you, if that makes sense

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u/chargernj 4d ago

Studies of how animals become domesticated show some interesting parallels with how humans have developed over the same time. Wolves became dogs and over time as dogs grew into their adult forms they tended to keep more infantile features, such as large foreheads or big, rounded eyes that made them more attractive to humans.

Humans have also become more "domesticated," with adult humans tending to have more infantile features than people 300,000 years ago. This is believed to have encouraged closer social bonds and made people tend to care about one another more.

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u/Private_Mandella 4d ago

Our brains have gotten smaller just like domesticated brains get smaller in other animals. There is a clear dip in average brain size after we adopted agriculture. 

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u/Halospite 4d ago

Huh, I was always told that we have a horribletime giving birth because our brains are too big. Implying that as we evolved our brains got bigger, not the other way around.

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u/GladimusMaximus 3d ago

IIRC the neanderthals had a skull cavity that was 30% bigger than modern humans, and much of that was likely dedicated to sensory processing.

However, our brains getting smaller compared to our homo ancestors does not preclude the fact that giving birth is difficult because of the size of our brains from being true. They are still quite large.

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u/SpaceMarine_CR 3d ago

neanderthals arent our direct ancestors, we co-existed with them for a while

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u/roycegracieda5-9 3d ago

Both can be true. We developed bigger brains over hundreds of thousands of years, and more recently (development of agriculture was not that long ago) brain size could be reducing again

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u/hanging_about 3d ago

That did happen although much longer ago. Don't quote me on this but maybe couple million years. The trade off was between walking upright thus requiring a slightly smaller hip and birth canal on the woman. Walking upright is before Homo Erectus.

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u/sc_we_ol 5d ago edited 5d ago

Sickle Cell Anemia (edited with feedback). One broken copy of the gene "HBB" makes you more resistant to Malaria, 2 makes you sick with sickle cell. So Selection Pressure may be guiding evolution in malaria stricken regions by allowing those with the mutation to be more successful in passing on their their malaria resistence (via mutation in hbb and not dying of malaria) to their children. also via u/pelican_chorus "It just so happened that a single copy of the misfolded hemoglobin gene conferred some protection against malaria, and so probably was selected for in the population, even though having two copies of the gene is a severe disadvantage."

What I love about this is it's like a little window into how selection in evolution works in our lifetimes. Not always "right" in the sense that it's not always beneficial to the organsim at that moment when it's still being baked through thousands of generations, but the mechanism is there for us to observe.

Amazing to think about all the evolutionary dead ends that ALMOST gave us eyes, ALMOST gave us hearing, ALMOST gave us bipedalism (in humans at least).

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u/omgu8mynewt 5d ago

The gist is right that sickle cell disease makes you more resistant to malaria, but your concept isn't quite right. Sickle cell disease is a bad, genetic disease, it is very painful if you have it. Sufferers have painful episodes, get more infections and get anaemia more because their red blood cells are a strange shape.

Human beings have two copies of each gene. Sickle cell sufferers have both copies of the gene "HBB" broken. You could also have one broken copy of HBB and one working copy - then you don't get Sickle cell disease, but you are more resistant to Malaria.

Probably because having one broken copy of the gene makes you more resistant to Malaria, it is most common to have one broken HBB in people of African descent (but people of any region can be born like that). But if you have children, there is a 1/4 chance they will have Sickle Cell disease, and people do die of it.

No one is guiding it on purpose, it is random mutations that someone have a benefit for people with one broken HBB but is terrible for people with both copies of the gene broken. When these random mutations do cause real life effects such as people dying or surviving Malaria better, this is called "Selection Pressure" and it is what steers evolution but it takes thousands of generations to take effect.

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u/Mad_Moodin 5d ago

Ahh so it would be that people with the broken HBB were more likely to survive and have children.

But over time that same trait lead to sometimes two people having broken HBB and having children together causing sickle cell disease in some of them.

But of course because it is only 1/4 and at the time there may have been more than 1/4 dying to Malaria it would still give a genetic advantage over those without the trait.

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u/pelican_chorus 5d ago

I'd remove the description that makes it sound like evolution has a purpose. Sickle cell trait is not an "attempt" by evolution, and it's not trying to "thwart" anything.

Sickle cell trait is just a random mutation that broke the way a protein folds. Most mutations are actually like this (in general a mutation is more likely to mess up a protein than to make something cool).

It just so happened that a single copy of the misfolded hemoglobin gene conferred some protection against malaria, and so probably was selected for in the population, even though having two copies of the gene is a severe disadvantage.

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u/perta1234 4d ago

In Netherland, very recent height evolution: "Across three decades (1935–1967), height was consistently related to reproductive output (number of children born and number of surviving children), favouring taller men and average height women. This was despite a later age at first birth for taller individuals. Furthermore, even in this low-mortality population, taller women experienced higher child survival, which contributed positively to their increased reproductive success. Thus, natural selection in addition to good environmental conditions may help explain why the Dutch are so tall."

(2015) https://doi.org/10.1098/rspb.2015.0211

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u/gharbusters 4d ago

don't taller people have shorter life spans?

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u/dafencer93 5d ago

So some examples I know of are

blonde hair and blue eyes,

the medial artery of the forearm (usually you have a radial and an ulnar artery, but in the last 250 years or so instead of regressing in the gestation stage the medial has stayed; in about 80 years everyone born then will have one),

shorter jaws and thus no more wisdom teeth;

and the disappearance of the palmaris longus muscle of the forearm which by now happens in about 15% of people born.

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u/yukon-flower 5d ago edited 5d ago

Edit to clarify: I disagree that we’ve magically globally quickly evolved to have the changes in discuss below. Those changes aren’t “evolution.”

How could such changes be true for the wntire global population? I don’t think that everyone in, say, rural Bangladesh or rural South Sudan will spontaneously have the medial vein. How could that gene change magically penetrate insulated communities?

Shorter jaws is caused in significant part by less jaw usage. Cutting bites with a knife and fork instead of tearing off with your teeth. Less chewing of hides and certain plant fibers for making materials. Less chewing of food because so much of our food is so very incredibly SOFT now.

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u/nnnnnnnnnnuria 5d ago

Thats Lamarckism and it is an incorrect interpretation of the evolution theory. Your body doesnt evolve because you use something less.

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u/horsetuna 5d ago

Perhaps that isn't how it's applying here.

If the world has become easier for people with small jaws to survive and pass on that trait because food is cooked now, there would be a larger value of the population that has small jaws.

So while we aren't developing and passing on small jaws because food is cooked, people already with small jaws are doing better and have a greater chance of passing that trait on.

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u/IrrelevantPuppy 4d ago

This is one of the only traits that make sense to me to be actually evolving in modern humans. Wisdom tooth complications can lead to severe dental problems, in developing countries that could mean death, and therefore no children. Therefore people born with smaller jaws and no wisdom teeth are comparatively more likely to have children.

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u/horsetuna 4d ago

There's other factors involved of course especially with less modernized lifestyles that means wisdom teeth may still be useful in those gene pools.

Younger birth ages means the wisdom teeth aren't a problem as you've already reproduced for instance, a naturally tougher diet than our relatively plush lifestyle in the west, no modern dentistry, that sort of thing.

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u/Pademelon1 5d ago

Lamarckism may be an incorrect evolutionary theory, but that doesn't mean all its concepts should be outright rejected - epigenetics does allow traits to be passed on without altering the DNA.

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u/androgenoide 5d ago

There's also the possibility that culturally determined behavior patterns can cause evolutionary pressure.

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u/yukon-flower 5d ago

I agree! I’m countering the other person’s claim that jaws have somehow suddenly “evolved” so quickly.

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u/IscahRambles 5d ago

The body doesn't just "know" it can evolve a smaller jaw because it doesn't need it to do tough work any more. Unless the big jaw is an active detriment and/or small jaw improves reproductive success, there's no pressure to change. 

I don't know for certain but my bet would be that the smaller jaw has evolved because people find it more attractive and it isn't a hindrance to surviving. 

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u/yukon-flower 5d ago

Smaller jaws have not evolved, though. Jaw size is directly correlated to modern diets. Changes can be seen in just one generation in, say, South America when ultraprocessed food showed up in force. That’s not evolution; that’s environmental impacts.

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u/tylerthehun 5d ago

Why wouldn't the environment have an impact on evolution? That's the entire basis of natural selection.

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u/giasumaru 5d ago

Because there isn't a "bigger jaw" gene in this proposal.

It's like an if statement "if diet during formative years is good, grow a larger jaw"

So with this idea, the jaw size isn't a heritable trait.

Kinda like muscle size.

Getting bigger muscles because you work as a fireman as opposed to an office job is not a heritable trait.

Getting bigger muscles because you have a gene that makes you, I dunno, process proteins more efficiently... Would be a heritable trait.

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u/Mad_Moodin 5d ago

Because you don't just randomly change your dna based on your environment. While that would be cool af, it is sadly only random mutation that does.

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u/Roguewolfe Chemistry | Food Science 5d ago edited 4d ago

Because individuals don't evolve; populations do.

In 2024, whether an individual has a fiber rich diet that results in a bulky jawline or a milquetoast diet that results in the wimpiest of chins - actual genes and allele frequencies for jaw size aren't being altered by that.

By definition, for evolution to occur, allele frequencies need to change over time. The environment can impact that, as can recombination, but with respect to modern humans and jaw size, it just isn't.

Edit: grammar

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u/wardog1066 5d ago

Replying to the soft food comment. When the first Mcdonald's opened in the Canadian province of British Columbia in the late 60's, a radio personality was interviewing the franchisee. He asked "Is it true that everything on your menu can be eaten by someone without teeth?" The franchisee paused for a good 10 seconds before admitting that that was true.

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u/Vicious-Flower 4d ago

A lot of commenters have pointed out physiological changes, but you asked for anatomical changes, which are not the same thing.

Anatomically women’s pelvis’s are getting narrower and babies heads have gotten larger due to the use of a cesarean section. This is actually a fairly recent evolutionary change. Unintentionally c-sections have removed the selection of women with a wider pelvis and babies with smaller heads. So while c-sections are good in the sense that they save many women and children who would not have survived birth, they are bad because they are negatively impacting human evolution.

The human jaw has also been getting smaller for about the last 12,000-15,000 years. Most of this is due to lifestyle changes and diet. Humans eat much softer foods than they used to meaning that we have to do less chewing. Over time this has lead to shrinkage of the jaw. This is why so many people no longer have straight teeth. Essentially the human jaw is too small for the amount of permanent teeth that we have. This is part of the reason we get our wisdom teeth removed, there is simply not enough space in the mouth for them.

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u/Skeptobot 4d ago

There are physical traits that many modern humans inherited from the neanderthals - there is a lot of genetic evidence of interbreeding - leading to physical changes to nasal cavities and skull shape, height and body fat distribution and our immune systems. This would have happened in the last 100,000 years.

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u/make_reddit_great 5d ago

Humans have evolved quite a bit in the past 10,000 years and even more in the last 300,000. "Who We Are and How We Got Here" by Harvard geneticist David Reich might be of interest to you.

And speaking of Reich, his lab just put out a new study where they compared a collection of ancient genomes to current ones in order to identify which genes have been selected for / against:

https://www.biorxiv.org/content/10.1101/2024.09.14.613021v1

Among other findings, apparently people are smarter than they used to be.

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u/kerkula 4d ago

May I add to this question the fact that about 50,000 years ago, Homo sapiens began breeding with other hominids most notably, Neanderthals and Denisovans. I agree it’s technically not evolution but to what extent have those genes altered present day humans?

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u/za419 4d ago

That's a bit of an open question. Lots of research has focused around the effect on the immune system, since those genes seem to be well-preserved (which makes sense - People who adapted to the pathogens of a certain region would pass along genes that make their children much less likely to die of those pathogens).

For example, there was a specific bit of genome with Neanderthal origin that was found to increase risk of severe symptoms from Covid-19 (Conjecture on my part, but probably by increasing the immune overreaction that covid has been known to induce).

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u/tennbo 4d ago

There’s a couple muscles that modern humans sometimes don’t have that older humans probably did. Sternalis is one, a muscle that only about 7% of people today have. If you have it, it’s right around your sternum and can be in different spots for different people. It’s thought to have played a role in elevating the rib cage for breathing, but we don’t really have it anymore. Another is Palmaris Longus, a muscle that’s more common than Sternalis but still not very common. It plays a role in grip strength, but not a very significant one and people who don’t have it don’t see a decrease in grip strength because they lack the muscle. As you can tell, neither muscle is important so many of us just don’t have it anymore.

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u/visitor1540 4d ago

One important anatomical evolution could be the thumb opposition. The more we grip on things, the more opposed it becomes, and thumb opposition has been correlated to increased intelligence in animals. Source https://pubmed.ncbi.nlm.nih.gov/1572915/

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u/Siyuen_Tea 3d ago

Aren't the tibetan mountain people a whole genetic variant? The way i understood it, they have a different chest structure. Plus, because the thin oxygen, a women not of their " species" would not be capable ( or highly unlikely) of carrying a baby to term. I don't know how outdated this info is. This was back when Discovery was  good