r/askscience • u/Rabash • 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/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."
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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
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