Any radiation penetrating enough to get through an airtight wall or a spacesuit will be too penetrating to be appreciably blocked by melanin; it's mainly of use against lower-energy radiation.
No we would be pale like a freshly shaved chimp. As we gradually lost our hair we evolved to have darker skin. When we migrated out of Africa we adapted again to mountains and caves then became pale again.
The key points are both dark and pale skin are evolutionary traits once we lost hair. If you sweat you probably want light skin under fur.
And then you have polar bears, whose main problem is staying warm rather than staying cool or avoiding sunburn. They have black skin and translucent fur so that all of the sunlight is absorbed below the outer insulation layer instead of on top of it.
Also the parts of hair cells that would normally hold pigment are hollow rather than filled with pigment because an air void conducts heat less and thus is more insulating.
Not sure if you are joking, but that's by far the most probable option. Just look at civilizations living for millenia near equator, be it Africa, isolated islands in Indian ocean (ie Nicobar) or native Australians.
Planet was colder, and around equator you actually have quite habitable places even now, deserts are further from equator. But you get tons of light whole year in very stable pattern.
Presumably it also applies to humans, but only α and β rays, not γ-rays or cosmic rays. If a space suit or a spacecraft skin can't stop it, your skin isn't going to stop it either.
The article doesn’t say whether they are just black on the skin, or black throughout the body.
Melanin throughout the body could perhaps help protect a little against some ingested radioactive substances (given the mechanisms listed).
However I am guessing the the existing genetic variation was for skin colour, so only the skin colour was likely to be selected for (given the small number of generations).
(1) This is adaptation, not evolution, but it may be merely selection of a pre-existing color variant that already widely found in nature. We have the same exact variation of melanistic toads & frogs found in the US.
(2) They really don't know how many generations this occurred over, they have a measurement, and a measurement.
(3) The baseline wasn't built before the Cherynobyl event. As a person that has caught a great number of frogs and toads, their coloration in normal areas varies greatly based on the local Flora and sun conditions. The very dark / black frogs which are already found in nature, may have just reproduced better, instead of coloring adaptation being introduced. Frogs that live near asphalt and post-wildfire conditions would be expected to have better survival characteristics due to decreased visibility.
> it may be merely selection of a pre-existing color variant that already widely found in nature... very dark / black frogs which are already found in nature, may have just reproduced better
If this variant is being selected for preferentially, that's evolution: "Typically, we think of biological evolution as changes in gene frequency within a population over time – if, say, birds with genes that produce wide beaks went from being rare to being common over multiple generations."
It is a population that evolves, not an individual.
Selection of a pre-existing feature that already occurs in the gene pool is exactly how evolution works. There are only two things needed for evolution:
1) generation of diversity between individuals (see sexual recombination, V(D)J recombination, etc)
2) selection of traits
The fact that black frogs already existed at some frequency does not mean that the population did not evolve in response to radiation.
But you are right that radiation is not the only thing that might select for dark frogs.
So it would seem this gene for melanin already existed in the gene pool of these frogs - it's not like the radiation caused a mutation that led to this. So that's what makes it adaptation vs evolution? (where the latter would be an entirely new gene that arises that wasn't in the population before?)
They are not claiming that the radiation led to evolution of an entirely new gene..that would be unprecedented. You don't get "brand new genes" in that kind of evolutionary time frame.
Also, there is not single gene for melanin. Several genes are required for the ultimate effect that you observe as dark skin. A mutation in any of these genes, or in any of the transcription factors which control expression of these genes, could lead to observed differences in frog skin color.
FYI, "new genes" are usually the result of duplication of an existing gene (https://en.wikipedia.org/wiki/Gene_duplication#Mechanisms_of...). Duplicating a gene can be useful in and of itself by providing functional redundancy. However, the new copy is then also subject to its own mutations without affecting the original copy, and over time the two genes may diverge in function.
And existing variation in the melanin genes is enough! No need for mutation. The way to rapid evolution in animals is sexual reproduction. The stronger melanin genes can add up in children where the parents had only some. When the darker children are selected for, the genes that lead to less melanin become less common.
Tldr for those opting out of tracking: melanin protects from cell damage due to radiation, frogs found inside the contamination zone were darker than those outside.
Well it's not relying on evolution coming up with an entirely new chemical or protein, in this case it is increased expression of one the frogs already have. Still super fascinating to think we have innate, multipurpose radiation protection.
right, and the fun only really starts when the black frogs stop mating with the green ones; I don’t think that (speciation) was mentioned in the article
> our hypotheses about the "natural" speed of evolution are wrong
There's so much to unpack in that sentence! :)
In general, a layman's understanding of a complex scientific topic is going to be wrong but if we restrict "our hypotheses" to evolutionary biologists, then no. Between the (very popular) equilibrium hypothesis that a sibling linked to, microbiology, and the textbook cases of evolution during the industrial revolution [1], biologists have known for a long time that natural selection can be fast or slow.
Regarding "natural" and tying back into the equilibrium hypothesis: non-cyclical rapid changes to the environment used to be much rarer before humans began building civilization, so pre-historic evolution might have looked significantly different. Nowadays, all it takes is a single ship to accidentally transport an invasive species that will wipe out an ecosystem and leave only the ones best adapted to the new reality.
Last but not least, the "speed" of evolution is actually a combination of two orthogonal factors: the mutation rate and selection pressure. Natural selection can only select from the species that exist (i.e. the ones already surviving) so mutation rate is really what most people mean when they say "speed of evolution". Chernobyl is a very special case where the radioactive fallout increases the mutation rate, reduces lifespans by an average of 30% (IIRC) putting more pressure on survival to sexual maturity, and removes much of human interference from the picture. I wouldn't draw many conclusions on evolutionary biology from Chernobyl unless we plan on turning the entire planet into a fallout zone.
Punctuated equilibrium (https://en.wikipedia.org/wiki/Punctuated_equilibrium) is an evolutionary hypothesis that evolution is very slow, except when selection pressures change. If true, the average speed of evolution (in this case, of phenotype) is slow, but highly bimodal (i.e., breakneck or near zero).
Our perception may reflect the lack of surveillance and tracking of our entire environment. Marlene Zuk tracked [0] a trait's velocity in cricket populations of Hawaii that made them less able to attract mates, but also less likely to attract mites. That took 20 generations.
The "speed" of evolution is influenced by a multitude of things, time between generations and number of offspring being two of the major ones. For species like frogs where generations are quick and tad poles are plenty, there's a lot of shots in the dark for evolution to work with so it can happen quickly. For species like humans that take like a fifth of a century per generation and only really shove out 1 or 2 offspring and have a large steady population for genes to diffuse through, the process is a multi-millennia affair.
Fruit flies in a jar iterate fast enough if you want to try playing god for a while.
Yes it generally is. Look at this fragment where Nick Lanes (British Biochemist) talks a little about this. If you don't know Nick Lane, his books are fantastic. I highly recommend Power, Sex and Suicide.
Recommend reading: the beak of Finch. scientists detected evolutionary effects during one year period! this book published in twenty years ago. evolution work quickly sometimes,but don't towards same direction.
I'm aware of that. I used to dedicate a Firefox container to these sites so they can track between themselves, but that's basically private browsing with extra steps. Private browsing, an ad blocker, and a cookie manager for when I want to scrub a site/container is the best compromise I can find right now.
I care for my privacy, but the pressure of spyware is everywhere, at multiple levels, and the effort required to counter it completely is excessively asymmetrical.
Yeah directly against this site's guidelines I can't click on links anymore because they are so rapey. They want me to consent to anything in exchange for reading for 30 seconds? Do they have any idea what that word means?
Like going to do pagerank with consent cookies, filter anything with a consent cookie, and anything that links to anything with a consent cookie, see what's left.
This is exactly wrong. Lamarck believed in the inheritance of acquired traits (e.g. if you cut off a mouse's tail, then its babies would be born with shorter tails).
Darwinism, conversely, is about selection from within a range of traits already present (i.e. beak size).
These frogs come in a variety of colors. Dark colors have a better fitness for the highly radioactive environment. Those are the ones that reproduce. This is textbook Darwinian evolution.
Epigenetics - the ability to switch certain genes on and off without changing the genetic information (like commenting out certain lines of code) based on environmental cues.
I don't understand "Why pick the former when the latter works."
No one is picking anything, it's all happening simultaneously. An epigenetic solution would reduce selective pressure for a genetic solution, theoretically.
Because the former mechanism, for lamarkism, wasn't given, and Some kind of "genetic intelligence" is just a vacuous proposition, so why raise it. Your mention of epigenetics was a sensible suggestion in that at least it's known to happen (although whether it can control skin colouring is another matter)
And does that mean darker-skinned human beings are better suited for space travel?