The one question I’m inevitably asked after lecturing on evolution to a general audience is this: “Are humans still evolving?” What they really want to know, of course, is whether we’re getting smarter, taller, handsomer, and so on. Well, with respect to those traits I always say, “I have no idea,” but humans are still evolving, albeit in ways that don’t excite most people. I’ve posted about this twice (see here and here), and in recent times we have evidence for H. sapiens evolving to produce, in women, earlier age of first birth, later age of last birth and (also in women) increases in height in some places and decreases in others. Studies in the U.S., which haven’t been conducted elsewhere, show the recent evolution of reduced cholesterol levels and lower blood pressure, and an increased age of menopause.
The U.S-specific data brings up the question of whether even if the entire human species is not evolving in a given direction, individual populations or groups might be undergoing “divergent evolution” in response to their specific environments. And for that the answer is clearer: “Yes.” We’ve known this for some time. Tibetan and South American populations have evolved adaptations to low-oxygen conditions, pastoral populations (those keeping sheep, goats and cows for milk) have evolved persistent lactose tolerance (a trait normally turned off after weaning), and some African populations have evolved small stature, a trait thought to be useful in tropical environments. The smaller-stature trait is a bit questionable as an adaptation, but in all three cases mentioned above, researchers have pinpointed the genes responsible for the adaptive changes.
There are other cases of human populations adapting divergently to their unique environments, with genes for that adaptation tentatively identified. In a short “news and views” article in the latest Science (free access, link below), geneticist Sarah Tishkoff summarizes both the genetic data and trait data, producing the nice figure below showing where that evolution has occurred, which traits were involved, and which genes are implication in those adaptations. (Be aware that adaptations, even in these cases, are likely to involve more genes than are listed, as genes of small effect are hard to detect):
Tishkoff wrote her piece to highlight a paper by Matteo Gumagalli et al. (many collaborators!), which I’ve referenced below (link not free). That paper used population-genetic analysis of Greenland Inuits to discover regions of two chromosomes that seem to have experienced strong selection in the recent past. (We know this because we can see that those regions have increased in frequency compared to similar regions in other places.) Those regions also happen to contain genes involved in fatty acid metabolism; and the variants of the genes that have increased in frequency in Inuits are also associated with small stature and lower weight. (The small and stocky bodies of northern populations may also be an adaptation to reduce heat loss—Bergmann’s Rule, as observed in many animal species—or it could simply be a byproduct of a metabolism altered by selection to reflect a novel, fish-rich diet.)
So if you’re asked “are humans still evolving?”, the answer is this: “Well, there’s some evidence that our species is evolving as a unit for traits like age of reproduction, but there is much more evidence that different parts of our species are evolving in different directions, adapting to environments that are geographically different or changing over time.” Of course our culture has slowed some forms of selection, as doctors and dentists help people survive who would have been ruthlessly culled on the savanna. (I am one of these misfits.) But so long as there are genetic variants associated with different numbers of offspring, our species will continue to evolve.
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Tishkoff, S. 2015. Strength in small numbers. Science 349:1282-1283.
Fumagalli, M. et al. 2015. Greenlandic Inuit show genetic signatures of diet and climate adaptation. Science 349:1343-1347.
I think that the recent trend to use cesarean section in difficult births, and sometimes even electively when births aren’t expected to be difficult, could eventually cause evolutionary change, especially if the practice expands to the larger population. I can’t think of anything with more selective effect on human anatomy than the rigors of birth. It may be that in the future C-section will be the norm. It could lead to women having smaller pelvises and babies having bigger heads.
+1
That reminded me of this recent paper I saw, which implies the human pelvis is not solely under obstretical selection pressures, and perhaps not much compared to other factors. [I haven’t read it.]
“ABSTRACT
Objectives
Sexual dimorphism in the human bony pelvis is commonly assumed to be related to the intensity of obstetrical selective pressures. With intense obstetrical selective pressures, there should be greater shape dimorphism; with minimal obstetrical selective pressures, there should be reduced shape dimorphism. This pattern is seen in the nondimorphic anterior spaces and highly dimorphic posterior spaces. Decoupling sexual dimorphism in these spaces may in turn be related to the differential influence of other selective pressures, such as biomechanical ones. …
Results
MANCOVA analyses demonstrate significant effects of sex and body mass on distances in both the anterior and the posterior spaces. A comparison of the relative contribution of shape variance attributed to each of these factors suggests that the posterior space is more influenced by sex, and obstetrics by proxy, whereas the anterior space is more influenced by body mass, and biomechanics by proxy.
Conclusions
Although the overall shape of the pelvis has been influenced by obstetrical and biomechanical selective pressures, there is a differential response within the pelvis to these factors. These results provide new insight into the ongoing debate on the obstetrical dilemma hypothesis. Am J Phys Anthropol 157:428–440, 2015. © 2015 Wiley Periodicals, Inc.”
[ http://onlinelibrary.wiley.com/doi/10.1002/ajpa.22734/abstract ]
I think some people who ask “are we still evolving” mean something like “are we likely to speciate soon”, which doesn’t seem likely. That said, all these local adaptations are neat. Imagine trying to get them all into one person!
Since reproductive isolation is a necessary condition for speciation, it seems increasingly less likely for humans, given globalization and the elimination of restrictions on miscegenation.
I could imagine some cult deciding to deliberately engineer reproductive isolation into their offspring.
Stephen Baxter’s novel Evolution, which is basically a series of vignettes of mammalian evolution from 65 million BQ to the far distant future, has a minor, but interesting subplot about exactly this.
On the other hand, dispersal of human populations throughout the solar system would certainly create new selection pressures as well as new modes of isolation.
I’ve often joked about how if North Korea was able to stay the same for thousands of years, they’d eventually become their own sub-species of human.
…or when we’ll start developing supernormal mutant superpowers, or when we’ll start growing arms out of our foreheads, and so on.
It’s highly likely that those who don’t think humans are continuing to evolve also don’t understand Evolution in the first place.
One can envision a future in which human evolution stops dead in its tracks: one where we start intelligently designing our children. But anything short of that? We’ll keep evolving at the same glacial pace as always, towards nothing in particular save fractionally better chances at having grandchildren.
b&
It’s the potential for X-Men (the mutant superpowers thing) that I think a lot of people wonder about too. In fact I’ve had several young people ask me if I think it’s possible. Probably a few people at PCC’s lectures have the same thing in mind, but don’t come out and say it.
Of course, the most rapid human evolution in is bio-tech where technology is merging with our biological beings. This type of evolution can be planned and directed toward achieving specific short term results.
This is ‘evolution’ in quotes, since it does not involve changes in frequency of genes.
Sorry, you lost me. Genetic engineering does not involve changes in gene frequencies?
I think he means biotechnologists are not evolving more rapidly than other humans. Or something.
I’ve wondered how one would define “evolving” for humans and it seems to me that what would be necessary is to sequence every person on earth over many generations and identify the frequency of each base for each genomic location and look for a change over time, and that would be evolution.
The answer, I would think, would be yes, of course we’re evolving, that every living thing is always evolving. The rate is another question – fast for humans, I would bet.
In the sense of genetic diversity, my guess would be “yes.” In the sense of selection, my guess would be “no.”
Well, I think we have (as Jerry identified) eliminated some selective forces, so we are bending the selection process somewhat. It’s different than it has been in the past.
Tishkoff, S. 2015. Strength in small numbers. Science 349:1282-1283.
Not only not “free,” but the AAAS’ elitism is now so vulcanized that they won’t even toss the unwashed the bone of an abstract.
WT
Yes. But I will wait by going to it while at work (on campus), then I will have the article.
A few years ago, during spring, I met a Finnish exchange student who complained about the ‘hot temperature’ of 15 °C (59 ºF). She was only 160 cm (5’3″), so I guess she was adapted well to the cold environment of Finland. Almost all female Finnish exchange students I’ve met were quite small.
Ha! That’s the first time I’ve ever heard of 15°C described as “hot”!
One time, as a friend mine and I were bicycle touring in Scotland (don’t ask!), we pulled into a cafe, out of the 10°C rain (this was in August!), teeth chattering and ordered coffee — just for its heat.
The young lady at the cash register (dressed in layers of wool) responded to our incredulity at the weather with, “oh, it’s lovely cool out!”
Cool indeed it was.
These people up north truly have an iron constitution.
When your men wear kilts and no underwear, it’s a requirement.
I always remember a statistic from Scotland in the 1880s: enough legal whisky was sold that it meant every adult and child drank more than a pint/day. Whether it really warms you up I don’t know, but it either makes you feel warm, or makes it so you don’t care.
Holy cow. I hope some of that was meant for export.
That’s how much was sold in Scotland, so my assumption was it didn’t include export sales.
Maybe it was all glugged by Queen Victoria on her annual visits to Balmoral. Perhaps it keeps the werewolf gene in check? (Dr Who reference in case you didn’t know.)
I’m sorry, I don’t watch Dr. Who. I prefer The Musketeers, but season 3 starts probably somewhere in January/February. 🙁
I like the Musketeers too! Glad to hear there’s another season coming. But the new season of Dr Who starts tomorrow night! Can’t wait! 😀
It actually makes you colder, by dilating blood vessels in the skin and increasing heat exchange. But at first you feel warmer for the same reason – increased blood flow to the skin.
I knew it was something like that – good to have someone to explain the mechanics of it all! 🙂
Heh…we’ll go months at a time without the overnight low temperature getting anywhere near that cold, and it’s rare to have any extended period when the daytime high doesn’t get up to that. In the winter, that’s about where I set the thermostat. The heater rarely goes on, and I get chilly if it gets much below that.
b&
It takes a while to adapt to changes in temperature. Early this summer I felt uncomfortable at 80F, now it doesn’t bother me till I see 90F. I understand our blood thins for the hot season and thickens for the cold. Surface blood vessels dilate and constrict. But there seems to be quite a time lag.
I met an Alaskan native who had just come to the lower 48 in mid summer. He was struggling with temps in the 70s and 80s. I told him to give it a few weeks and see if he did not see an adjustment. Unfortunately, I never met him again so I don’t know if my prediction held true.
That sounds like heav- er… very comfortable! 😛
…but not when the overnight lows don’t dip below 90°F / 32°C for months at end, and the daytime highs stay north of 110°F / 43°C for almost as long….
b&
I would not survived to the age of reproduction in the era before antibiotics.
Saved my life at least once. (The biggie was adolescent dental development – or its lack, rather – that led to an adult infection.)
Me too. I wonder how many of us are actually miraculous survivors due to penicillin.
The first prescription I ever filled for myself as an adult was for penicillin for a toothache. It was merely painful and bothersome…but, in retrospect, I realize it may well have been lethal in an earlier era.
b&
This reminds me of the “Turkana Boy” fossil, (early Homo erectus). As I recall the cause of death was likely a severe tooth infection at the age of 12 years. It’s probably likely that that was the cause of a significant percentage of hominin deaths. Whatever natural resistance our immune systems possess today is thanks to the thousands of early deaths of our ancient ancestors. Antibiotics is now undoing that selective force creating a race more dependent on technology.
This very interesting article raises a couple of questions that have puzzled me for a long time. The main question is: what is it that distinguishes human beings from other species? In other words, what is the definition of a human being? For example, is it scientifically proper to classify a Neanderthal as a human being? Related to this, I wonder if it is possible in principle if not in practice to determine in Earth’s history when a being emerged through the evolutionary process that could be called human when his/her parents were somehow not human.
As my questions imply, I know next to nothing about the details of the evolutionary process. I have not been able to find answers that a person such as myself could understand. I would like to be able to answer these questions when confronting creationists.
That is one for specialists here, but the questions and answers depend on who you are asking.
For anthropologists, humans are more or less associated with Homo, which is an undecided number of species. And no, there isn’t any good definition for Homo, even if anthropologists tend to recognize the fossil species (i.e. based on morphology rather than species barriers).
“What he most wanted to find were fossils that could shed light on the primary outstanding mystery in human evolution: the origin of our genus, Homo, between two million and three million years ago. On the far side of that divide are the apelike australopithecines, epitomized by Australopithecus afarensis and its most famous representative, Lucy, a skeleton discovered in Ethiopia in 1974. On the near side is Homo erectus, a tool-wielding, fire-making, globe-trotting species with a big brain and body proportions much like ours. Within that murky million-year gap, a bipedal animal was transformed into a nascent human being, a creature not just adapted to its environment but able to apply its mind to master it.”
[ http://news.nationalgeographic.com/2015/09/150910-human-evolution-change/ ]
Re the species definition, I understand it in broad terms like this:
If you can answer where on a tree a branch starts, you can point to a specific generation and say where a species starts. Cut a tree and study branch formation. Does a branch start where you cut it at the tree? Or does it start deep within the trunk where the branch fibers start to grow?
In reality there is an evolutionary continuum, every generation changes about as much as the others (at least over scales of a few generations). It would be artificial to try to claim a discontinuity in a continuous process, so it is at the same time impossible and uninteresting.
“And no, there isn’t any good definition for Homo, even if anthropologists tend to recognize the fossil species (i.e. based on morphology rather than species barriers).”
– And no, there isn’t any good definition for Homo, even if anthropologists tend to recognize the fossil species (i.e. based on morphology rather than species barriers) when they see it.
I should also note that we are as “apelike” as other apes are. ‘More’ in fact, or at least more monkey like, because other modern apes are in some ways more specialized than we are. (Knuckle walks, et cetera.) They mean “other-ape like”. =D
By one definition we are the same species as Neanderthal. If two populations can bread together and produce viable offspring, then they are the same species. Genetic analysis of Neanderthals allows us to detect a few percent of Neanderthal genes in non-African modern humans.
Even if we could line up all of our ancestors it would still not be possible to point to a single individual and say ‘this was the first Human Being’, unless we chose an arbitrary definition designed to give that result. That is the consequence of many accumulated, mostly small changes in many characteristics over very large numbers of generations of variable populations (which complicate things further by sometimes interbreeding).
To get some idea of the scope of the problem you could try the review paper by Daniel E. Lieberman, David R. Pilbeam, and Richard W. Wrangham: The Transition From Australopithecus To Homo https://www.fas.harvard.edu/~skeleton/pdfs/2009b.pdf
As I pointed out over on Smilodon’s Retreat, this paper concerns itself with trying to illuminate the behavioural differences between Australopithicus and Homo; changes in life history, sexual division of labour, language, cognition, and material energetics, and the impact these had on the emergence of hunting.
It’s been cherry picked by Casey Luskin, who misrepresents it as saying the opposite of what it really says. But the thread http://www.skepticink.com/smilodonsretreat/2014/04/02/its-still-a-dog/ shows, I think, that there is little chance this sort of evidence will change a creationists mind. Even with the text in front of them showing that their leaders have lied to them. That there was gradual evolutionary change in the fossil record. That Australopithecus and Homo blend sufficiently that there is no clean transition between them, they continue to reject and misrepresent the evidence, shift goalposts, throw out false equivalencies, and are morally outraged that everybody doesn’t just bow their heads and agree with them. In the short term the best you can realistically hope for is to inform neutral onlookers.
Fascinating post, Jerry.
Yesterday, I read a related article: “Directional dominance on stature and cognition in diverse human populations.” Link:
http://www.nature.com/nature/journal/v523/n7561/full/nature14618.html
Their concluding clause: “[T]his study provides evidence that increased stature and cognitive function have been positively selected in human evolution, whereas many important risk factors for late-onset complex diseases may not have been.”
Fascinating article, and I think I will later use it. Thank you for this.
The link above is behind a paywall, but here you can see the abstract.
Something I’ve wondered about H. sapien evolution–there is a small percentage of Neanderthal DNA found in the genome of modern humans from some areas, and it perhaps had some survival advantage in, say cold climates? If it ceases conferring any survival advantage, and if populations with and without this Neanderthal DNA interbreed, should we expect the frequency/percentage of Neanderthal DNA in H. sapien to decline, maybe eventually become undetectable?
Reblogged this on Science Geek and commented:
An eternal question by almost everyone – Are humans evolving or are we at an evolutionary equilibria (if that even exists). Jerry says we are evolving still. An interesting read indeed !!!
Given how much the human environment has changed over the past 10,000 years, it would be difficult to imagine our genes could still be close to some previous equilibrium.
I’m just now reading Niles Eldredge, “Extinction and Evolution”. He and Steven Gould promoted the idea of punctuated equilibrium which suggests that widespread extinction events precede rapid spurts of evolutionary change. His comment about hominin evolution is to note that the growth in brain size(for example) was not gradual over 6 million years, but held fairly constant for each defined species for long periods. So, “still evolving” seems to have something to do with some extinction event triggering changes. Are we modern humans the product of some general extinction event? I feel it might better be described in the traditional language of rapidly changing environment.
I recall data stating that men with criminal records have more than twice as many children as men without. Given that some predictors of criminality – such as low IQ, impulsivity and aggression are inherited – the implication is that the speed with which we are evolving is accelerating, but not how we would like.
It seems to me that those traits have always been more successful (in biological term) in human history – that they have always been selected for, so perhaps it would be better to say that the pace of evolution in those traits is steady.
The implication seems to be that in 5,000 years or so, humanity will include nothing but misfits and sociopaths. Chaos will ensue and the world will be taken over by another species of animal altogether. Any idea which ones?
Or perhaps the chaotic phenotype would be self limiting. The men with criminal records will die young driving motorcycles into bridge abutments and whatnot, leaving the rest of us to breed our brains out.
Would this also apply to Republicans( especially the prez candidates)?
One might at least wish it were true.
I wonder what evolutionary implications there are in what I subjectively perceive to be the increased short attention span/attention deficit syndrome manifesting itself during the last 10-20 years, at least in part due to the borderline obsession with portable electronic digital devices.
If the current generation can’t maintain enough concentration to conduct reproductive activities, I suspect their infertility will result in a restoration of normal attention spans in the next generation, and perhaps even wider fingers incapable of navigating the digital devices.
Since a fertilization event takes only a few minutes, I expect that short attention span is not going to be selected against, unless those children of short-attention-span people don’t make it to reproductive age for some reason.
The linked Science paper on Inuit genetics will be interesting to read carefully considering that recent studies like this one from last year’s Canadian Journal of Cardiology (and other prior to it) have found that, in fact, Inuit populations have coronary artery disease and heart attacks just as much as non-Inuits.
Oops, sorry abstract only:
http://www.onlinecjc.ca/article/S0828-282X%2814%29
Inuit eating traditional Inuit diets? Or Inuit eating westernized diets? I’m under the impression that traditional societies had many fewer “diseases of civilization” (diabetes, obesity, Alzheimer’s, coronary artery disease) than they now do, having started to eat westernized diets, especially involving lots of starch and sugar, and think I have a fair amount of scientific evidence to back up this impression, but this is one area I really don’t want to get wrong, and would be happy to read more relating to the question.
sorry for the bad link, it’s here http://dx.doi.org/10.1016/j.cjca.2014.04.007 or PMID: 25064579, and an earlier study here PMID: 16277122
As I recall the Fodor et al study did attempt to estimate CAD in Inuit before the change to a more westerized, and I think the whole topic is still controversial. Quickly scanned the Science article above and doesn’t really go into CAD at all.
Selective pressures have changed dramatically for humans, especially in the last couple of centuries. And this inevitably causes evolutionary changes. Medical progress allows procreation despite having features which would have been eliminated by selection in the past. We have to expect human evolution to move towards an opposite direction of what occurs in nature. There will be more and more people who need technical or chemical support in order to ‘function’ properly. Human kind is genetically deteriorating.
On the other hand, we are just on the verge of a new era of modifying DNA. Genetic errors will be patched up in utero. No more near nearsightedness, crooked teeth or baldness. The future is bright for the human genome.
This will affect a very small percentage of the world population – those who can afford the technology. It will have little if any effect on the human genome as a whole unless the birth rate is much reduced in poor countries and then a way is found to economically provide the technology to all people.
Initially, yes. Like any cutting edge technology, it will, at first, be a costly endeavor to make the first few corrections. But, I think in time it will “trickle down” (if I may borrow that damaged term) to a wider proportion of humanity until it is as routine as eye drops and immunizations.
“Deteriorating” implies that there’s some universal standard of genetic goodness. There isn’t. There’s only adaptation to the immediate environment.
Our environment now includes optometrists, pharmacists, IVF, and a host of other novel survival and reproductive aids. Why shouldn’t we adapt to exploit those aids? And why call it “deterioration” if we do? That’s how evolution works.
sub
late to the subbing. Not sure how I missed this before!
I tend to contemplate the things that seem to be forgotten in the melee that is Evolution, and it’s progress. What spanner would have to be thrown in the works that could slowly bring evolution to a halt? What wrong turn could possibly bring such a scenario into play?
There is no progress in evolution, so that has not been forgotten – it has no relevance.
Evolution cannot be brought to a halt, neither rapidly nor slowly, since that would require that:
A. no mutations ever were to occur during DNA replication before meiosis
and
B. that environments remain exactly the same
neither of which is possible for us to control