By far the most frequent issue I’m asked about when giving public lectures on evolution is this: “Are humans still evolving? If so, how? Where are we going?” The short answer is “Yes, we’re still evolving, but not in ways that excite most people.” And what answer you give depends on whether you’re talking about whether we’re evolving right now, are referring to the recent past (about 10,000 years ago), or whether you’re talking about the species evolving as a unit or whether different populations are evolving in different directions.
Rather than reprise all the answers, I refer you to a few posts I’ve written about this question (here, here, here, here, and here.) The answer is that most recent human evolution has involved different populations evolving in different directions (for example, lactose tolerance evolving in pastoral populations, light skin pigmentation evolving in populations farther from the equator, selection for the sickle-cell allele in malaria-infested African populations—though not evolution, since it has led to a situation in which gene frequencies ultimately reach an equilibrium—and selection for genes allowing low oxygen tolerance in Tibetans). Those are all forms of selection sussed out not by looking at differential reproduction of individuals, but at the genetic signature of selection that acted within the last few thousand years in portions of the DNA. As far as “real time” selection measured by looking at offspring production, such studies are again limited to one population (in the US); those show evolution for reduced age of first birth and increased age of menopause in women, and for reduced levels of serum cholesterol.
The video below talks mostly about “ancient” selection (still a good example for those in the know, but one that creationists don’t accept because we weren’t around to see it happen), and about sickle-cell anemia, which is selection that hasn’t led to evolutionary change. (One exception: the sickle-cell allele is decreasing in frequency in US African-Americans, since they don’t experience selection for malaria resistance.) The allele for HIV/AIDS resistance is speculative; I’m not sure we’ve actually seen this allele increase in frequency in Africa.
There are no howlers or blatant mistakes in this video, and it is useful in pointing out that scientists have indeed acquired good evidence for natural selection in our species. But the whole series has suffered by being limited to 1.5-minute videos, severely reducing your chance of absorbing anything.
I agree the series seems full of errors as if they didn’t consult an expert. However, I suspect the net effect of the series is positive in that it exposes many people, who are without a clue, to the basic idea of evolution in a fun and friendly way.
It’s okay to make videos.
There’s a substantial body of research that shows why videos, particularly YouTube videos aimed at younger audiences, need to be limited to 75 to 90 seconds. If the runtime says 4 minutes, it won’t even be started.
The discipline to be meaningful and/or persuasive in such a short time frame imposes difficult burdens, and occasionally requires tradeoffs, such as breaking the subject into a series where each segment teases the viewer to see “what comes next.”
This is not to say NPR should be excused for substantive errors, but they deserve some sympathy for the challenges built into the task.
I have enjoyed this series, and I think it’s important to keep in mind the intended audience. We who are more immersed in this topic, or the sciences generally, tend to be in a bit of a bubble. We’re sick of hearing “Why are there still monkeys?” since we’ve heard it a thousand times, but we have also been exposed to the answers many times. There are plenty of people who are hearing or asking the question for the first time.
It wasn’t too many years ago that I was asking some of these questions myself. And the brief answer “There are still monkeys because we share a common ancestor, like different branches of a tree” was exactly what I needed to hear, and instantly clarified it in my mind. It was only later that I pursued the question in more depth.
This is a teaching series intended for children, and I think it does its job well. Of course, I am speaking as a layman, not as a scientist or teacher, so it’s always possible I don’t know what I’m talking about.
I doubt any “way” we might evolve would excite most people. Even if we were to wind up with remarkably different morphology at some point in the very distant future (assuming we have that kind of time), the changes will be too gradual to be “exciting”, or, indeed, even noticed (by which I mean we can’t “notice”, or predict, that a given small mutation will eventually lead to some larger change).
I have read (but don’t know for a fact) that the average human brain size has shrunk over the past 10K years. Perhaps it is because body size shrunk too, but wouldn’t that be an exception to Cope’s law? Some days I think the trend might be accelerating.
Well, I am not a biologist, but it seems to me that even if human evolution was accelerating, it’s still going to be at too slow a pace for us to be able to make predictions that would excite the average person. We can only detect the change in brain size (if true) in retrospect. I think it’s safe to say, non-biologist that I am, that we can’t say what kind of change in size our brains might have undergone 10K years hence. And 10k years is a short period of time, evolutionarily speaking.
Computer cpus have shrunk in size by orders of magnitude in just the past few decades but deliver processing power many magnitudes greater than before.
I think human brain size is a pretty useless, and even silly, metric for describing rates of human evolution.
If it were true (and I doubt that it is) that human brains are shrinking in size and increasing in power–a sort of biological Moore’s law–it would be a most interesting fact about human evolution.
I think it’s true that domesticated animals tend to be less “intelligent” than their wild cousins (wolves and dogs, for example). Could it be that by domesticating ourselves, we’re making ourselves stupider? (I’m only half kidding.)
Somewhat out there, but if our evolution can be said to have more or less stabilized in the Darwinian sense (natural selection), might we be on the verge of a different type of evolution, say Lamarckian evolution?
Meaning, will the time soon be upon us in which our technological prowess further integrates our biology with machine-like intelligence, processing and mechanical capabilities, something along the lines of hard drives that expand our brains, connectivity to a hive mind, Borg-like capabilities, machine augmentation of our senses and the like…so that our evolution shifts from natural forces in the environment (Darwinian) to Lamarckian forces say, we want a more powerful brain we slap in more memory and faster processors or what have you as they become available, completely bypassing natural forces.
Or even further out there, might the time be at hand in the next few centuries where we create our replacements all together, say a higher-order machine intelligence that ends up replacing us all together in the ultimate act of evolution?
Carl Kruse
We have been morphed by our technologies. We have become taller due to better nutrition, and generally heavier as well due to over-nutrition.
A while ago I was looking at my old Kindergarten class photo, and was quite surprised at how skinny everybody was. The legs of American children looked like tiny toothpicks.
But is that really evolution? If children today weren’t over-fed, their legs would still look like toothpicks. Seems to me that’s just a superficial function of how much food parents give their kids, and not reflective of genetic change.
No, it is not evolution. An appropriate term is ‘norm of reaction’. That is, phenotypes that change due to environmental influences.
Evolution is a change in the frequency of genes in populations. That is brought about by things like genetic drift and by selection.
I think of that as ‘social co-evolution’, since the individual changes doesn’t inherit. Epigenetics show, in my opinion, that lamarckian evolution doesn’t take even if it rides on darwinian evolution, it is too weak a mechanism. (E.g. the lamarckian changes disappears after 1-3 generations.)
When (or if, but CRISP derived systems may become precise enough) we start with personal genetic engineering we have another situation. Mostly new alleles will take if they are darwinian though, so I would think that is “artificial variation” more than anything else.
But I am no biologist.
Oops, darwinian selected alleles I mean.
Also, it is CRISPR/Cas (for “Clustered regularly-interspaced short palindromic repeats” and the Cas protein mechanism.).
Yeah, no biologist here!
I have been keeping my eyes on the use of CRISPR in biotechnology. The system is pretty amazing, and once it becomes generally known it is going to garner a lot of buzz but also woo.
I read piece by a journalist who visited a large lab in, I think, the Center for Disease Control. In each sub department there were already people working with CRISPR or were planning to incorporate it. They said it was a big breakthrough that should speed up research significantly.
It’s really something to watch.
Here different areas looks at this differently. E.g. we have “statics” vs “dynamics” in mechanics, but we don’t have ‘thermostatics’ for thermodynamic equilibrium despite that the latter often are handled analogous to statics.
I would give this as wide a slack as possible. As the article notes, changing the environment changes or removes the equilibrium.
Some of the differences are historical reasons, I’m sure. As we learn sciences becomes more integrative.
IIRC most Europeans today have alleles related to improved resistance to plague. If evolution is change in allele frequency over time, I would guess that would count. But as Jerry says, it’s evolution ‘not in a way that is interesting to most people.’ Most people want to know if we’ll grow third arms or something like that.
Another place to look for changes in allele frequency would be in ‘broken’ genes and areas where selective pressure has relaxed. Eyesight is an example that springs to mind; good eyesight is probably a lot less correlated with sufficient calorie intake and mate choice than it was in the prehistoric, so we might expect that alleles related to eyesight have changed in frequency because a larger variety of different versions of them are now equally ‘fit’ (compared to the past).
Reblogged this on The Logical Place.
Re: “selection for the sickle-cell allele in malaria-infested African populations — though not evolution, since it has led to a situation in which gene frequencies ultimately reach an equilibrium”
Technically correct perhaps, but it is unlikely that any malaria-infested human population ever reaches equilibrium (e.g., because of migration of non-sickling alleles into those populations). Hence selection and evolution should occur in any malaria-infested human population (unlike a population that has reached equilibrium, where selection operates every generation because of heterozygote advantage, but evolution does not occur because allele frequencies don’t change:
p=t/(s+t) and q=s/(s+t)
And, as Torbjörn Larsson already concluded at 12:21: Yeah, some biologists are indeed here, and greatly enjoy reading the posts and the comments.
Re: “The allele for HIV/AIDS resistance is speculative; I’m not sure we’ve actually seen this allele increase in frequency in Africa.”
I discuss this example in Chapter 6 of Evolutionary Analysis. The CCR5-delta32 allele, which confers on homozygotes resistance to most sexually transmitted strains of HIV-1, is virtually absent in Africa. Where the allele is common, in northern Europe, HIV infection rates are low. While it is theoretically possible that an HIV epidemic in a population harboring the delta32 allele could lead to measurable evolution, it doesn’t seem to be happening in any actual population.
Another case where folks behind the video might have consulted an expert.
Furthermore, the video omits an example measurable contemporary evolution in a human population. Three extended families in Iceland harbor an allele of the cystatin C gene called L68Q. 200 years ago, carriers of the allele lived just as long, if not a little longer, than their non-carrier spouses. At present, however, they die of strokes before they reach their mid-30s. From 1905 to 1985—about 4 generations—the frequency of L68Q in the Icelandic population fell pretty much exactly as predicted by basic population genetics. See Chapter 14 of Evolutionary Analysis.
The body is probably not evolving thanks to human adaptability. There is no selective advantage anymore in inheriting good body parts because of human adaptability. Adaptation is no match for adaptability as adaptation takes time and adapting or adjusting, by comparison, is instantaneous. In humans adaptability is the thing. The question is the provenance of adaptability. If it is the brain then there is the potential for evolution of the brain. If adaptability is the product of mind, that would not be the case.
I hadn’t thought of it that way, but is is a good way of expressing it. “Mind” in this sense is equivalent to culture. But . . . do you believe that the intended or unintended consequences of mind/culture could affect survivability and thus act upon the environment if not the brain?
“The question is the provenance of adaptability.” Quite.
Elsewhere on this blog, I used duck “domestication” (enslavement) as an example of the effects of culture, a large part of provenance, of context.
Culture, of course, abhors nonconformists, and historically eliminated them upon recognition. Such “slings and arrows of outrageous fortune” must needs to affect genes as well as (I don’t like this word, but I’ll use it just this once) “memes.”
Culture (e.g., “modern medicine”) has insulated the “unfit” from death to a significant degree, thus preserving genes that might otherwise have been relegated to the dustbin. I await evidence from my betters that indicate this process has resulted in perhaps greater diversity (and thus resilience or vulnerability?) in the human population.
Ultimately, environment will act (is acting–e.g. skin cancer) on that population to a greater degree, when the cultural juggernaut runs its course and the population is reduced to the point that said insulation is stripped away, and adaptation or extinction follows.
“Nature has shrugged off countless species in the history of the earth, and she will shrug off Homo sapiens with no more concern than any of the rest.” –Louis B. Ziegler
God is indifferent.