Why Sex? Biologists Find New Explanations
quantamagazine.org
quantamagazine.org
I wonder how convergent evolution [0] fits into this? Maybe one form of reproduction leaves a large niche open for another type of reproduction to fill in.
Could it be that there was sexual reproduction first and asexual reproduction came later? We always assume the other way around. But maybe conditions were initially always stressful and only after conditions improved (I am thinking of conditions on Earth when these single cells organisms were evolving) did asexual reproduction start.
Last question, is meiosis and mitosis the only two way to reproduce? I had never really though about it until now.
GP answer is a valid example?
Well, from a high-level view the only way a cell can make more cells is to divide, and if it divides it either makes a copy of its genetic material first, or gives half of it to each daughter cell. So in that sense, they're the only two ways possible.
From a more detailed view, I wonder if the machinery of meiosis is evolutionarily the same in every sexually-reproducing species, or if it has evolved more than once. My guess is only once, because it has a specific sequence of events which is always the same.
Ignoring the idea of three-way (or more) genetic swaps, which would be like another type of meiosis, what if there were other ways?
What if there was a "carbon copy" or "embossing" technique where a cell bumps it's genes up against other's genes, and through some process yet to be determined , the other's genes are "nudged" into conforming to the shape of the cell's bumping it?
Sort of like picking a lock.. you bump up against each cylinder enough times until it falls into the shape you want it to. No splitting of chromosomes, or transfer of actual genetic material needed.
Of course this is a pipe dream but I'm just imagining here.
Right here at home though, if you want a life-approximating thing that actually does reproduce that way, you're in luck. Prions are proteins (a type of biological molecule) that make more of themselves in pretty much that way. They arent alive and they arent cells, but they reproduce by bumping into normally shaped proteins and making them be shaped in the same way. They cause all sorts of terrible diseases like mad cow and tend to be incurable since, well, theres really not much to kill or stop, it's just a protein, making other proteins look the same way, very fascinating and very scary - there are hypothesis that suggest prion like processes could be involved in neurodegenerative diseases like alzheimers.
Unlikely. You can't mate with copies of yourself unless there are already multiple copies of yourself floating around.
I like the story they present in the article. For simple organisms, it's fairly inexpensive to let defective individuals die off. As organisms get more complex, it starts to become more costly to allow defects in the genetic code to persist. Then it becomes worthwhile to perform "integrity checks" to correct errors in the data as it's being copied.
If a population of organism is put into an environment conducive to a lot of data corruption, then the ones who are want to perform these checks are the ones who end up surviving.
You could imagine that when higher complexity organisms are exposed to high-stress environments, it would help establish their population's ability to sexually reproduce. The ones who aren't doing it will tend to die off.
Then as the complexity increases further, the genetic complexity itself can be a permanent endogenous source of high stress. The organism then loses the ability to produce asexually because it's no longer needed.
Sexual reproduction promotes genetic complexity because it allows us to survive while having more complicated genes. The recombination and mixing-and-matching only helps further the process along.
Asexual reproduction doesn't require copies of "yourself". Plants can self fertilize and they are some of the most complex organisms to do it and you probably know this.
Can you rephrase that statement?
We don't know if early replicators were inside lipid membranes or not. If they were in the goop they'd be floating with their clones and siblings.
Seems like it would be a natural next step for single cell eukaryotes to have a similar mechanism to fix bad DNA, especially given the much longer genomes of eukaryotes, which the article discusses without mentioning bacteria.
By the time you get to multicellular creatures, this gets even more important and leads to males, who pass on only nuclear DNA, and females, who pass one nuclear and mitochondrial DNA.
Practically, this means that getting proteins from elsewhere isn’t that selected for, while better regulation is. It’s a complicated subject, but that’s partially why there is so much “junk” dna in multicellular eukaryotes (single cellular like yeast are still pretty efficient)
Probably off topic, but I didn't know this was not a commonly accepted explanation. When I went to school (maybe middle school) in Vietnam in the early 90s, I was taught this. My biology teacher said this explains why marriage between closed relatives is not recommended because it leads to less diversity, and a bad gene would have chance to manifest.
Turns out, in a stable lab environment, hermaphrodites were more efficient. However, once you started changing the environment populations with males could always adapt faster.
Well that explains a lot.
In all seriousness, I find that the idea in the article raises another question. If mating can increase individual fitness by sharing something, how is that explanation of sex different than being a member of a social group? Social species take the idea even further. Is sex simply the building block for social behaviors, and more sophisticated adaptations beyond sex are now available?
There's also a misleading phenomenon where many of the fields whose "experts" chime in on these questions are called evolutionary psychology or behavioral genetics, making you think that these fields are related to biology and enjoy the same methodological standards of rigor as well as the same consensus from biologists. In reality these fields approach the questions from psychology, and that one field is known for having a bunch of practices, biases and motivated reasoning that'd make many a biologist reluctant to touch it with a ten feet pole.
It's very elegant to see the sleight of hand in action: someone makes a claim about sex, arguing it's a biological reality, and when challenged backs up their claim with a psych paper from a field that disguises as one from biologists and pretends that his claim enjoys a widespread consensus among actual scientists (as opposed to just psychologists). Hence, the claim isn't ideologically motivated, it's just science. Beautiful
I think there's a difficulty in that you can't just do biology from your garage, even bioinformatics. The standards have shifted, and most of the low-hanging fruit has been picked. You either need to generate original data yourself with costly experiments, collaborate with people who have done so, or explore enormous amounts of data with costly compute. To meet these requirements you need to be affiliated to an institution, i.e. work within the system. (An exception would be Googlers and other such people who already have access to the compute for some reason)
Perhaps the whole thing is ripe for disruption, but so far all I've seen is repeated variations on xkcd #1831.
Right now, with all the COVID type articles being posted, it feels a bit like that. I'm not a trained virologist, and I dont know how many trained virologist there are on HN. But a basic perspective on what is the diagnostic test (I've done plenty of QPCR), what is primer design, what are antibody tests, and basic virology like what does it mean to be an rna virus, how is remdesivir supposed to work, etc tends to be missing, and I think k people with my level of experience can provide that. I've studied enough healthcare management to know the terminology at least and be able to discuss a placebo controlled trial versus not, and there are a lot of people with that level of basic knowledge than can contribute. And I've seen those sorts of explanations that are quite good. I've also noticed some pushback from people with at least a basic level of statistical/epidemiological training to the narrative that the risks of COVID are overblown, with discussions of exponential growth and SIR models. There are a few glimpses buried on what can be a pretty large initial onslaught of nonsense of actual biological knowledge. I dont think you need 50 years experience to provide that, though of course that would make the perspectives that much richer and deeper.
Yea I’m around biotech forums quite a bit and it is just as bad from a technical side. However, people on HN and tech tend to be better at identifying how technology enables things to happens, which is interesting to me.
The main thing to learn from this is you can't really talk about this stuff because people don't want certain things to be true. Biologists tended to talk about this stuff openly with me after a few drinks. They dare not speak about it most of the time.
The crux of the matter (and potential controversy) is not about sex differences in plants or C. elegans. Most biologists I've met who study algae or polar bears usually limit their expert opinion on those species. It's really about transposing such knowledge to humans, where we don't have that level of bottom-up insight for a variety of reasons ranging from "humans are complicated", "most of what works in other species doesn't work in humans" (see: 99% of drug trials) to "you can't just open up people's brains to see what they're made of".
Isn't the point of doing animal trials that they are "close enough" for most things to deliver good results? I.e. "if you can't do it in mice, dogs and pigs with your proposed medication, you probably won't be able to do it in humans". They're close enough that xenotransplantation is actively considered. "Humans are so special, everything we learn about anything that isn't human does most likely not apply to humans, so don't you dare even suggest that" just sounds strange to me.
Animal trials precede the first (Phase I) clinical trials in people.
93% of drugs that make it past animal trials and into Phase I clinical trials fail to make it all the way to final approval:
https://blogs.sciencemag.org/pipeline/archives/2019/05/09/th...
It's also not clear how many drug candiates we're missing out on because animal models give false positives for toxicity in humans. Compounds that are extremely poisonous to experimental animals may be tolerated much better in humans.
Humans survive exposure to TCDD at levels that would be more than 50 times higher than the lethal dose in guinea pigs:
https://en.wikipedia.org/wiki/2,3,7,8-Tetrachlorodibenzodiox...
Acetaminophen is a deadly poison to cats even at modest doses.
It's impractical and unethical to try novel druglike compounds in humans right away, so we may not know how many premature rejections come from animal models until/unless we're able to grow whole human organs for drug testing.
And keep in mind we're talking here about behavioral differences driven by possibly the most complex organ that diverged the most from other animals'.
Yes. Studying biology is like reverse-engineering extremely complex, constantly changing microscopic systems which developed over thousands of years. Molecular biology in particular is prohibitively expensive. It's just not something people can play with the same way we play with computer programming. A fully equipped laboratory is required to perform even the most basic experiments. Even more resources are required in order to produce original work.
This also causes difficulty in reproducing published results. It's easy to verify that the laws of physics hold true. It's not so easy to reproduce an expensive 10 year long double blind clinical trial.
In this case, biology has a bunch of details, many still unknown, and problems look easy until you get into the details.
This is very strange because in technology threads where actual experts chime in, no one acts like that. People share their experiences about using such-and-such stack, sometimes with very strongly worded and passionate opinions but never with the pretense of scolarship or "quest for truth". Imagine how bewildering it'd be if people cited publications from "The Journal of Serverless Stacks" (IF=1.4) in lieu of experience sharing.
I agree that it can be annoying when armchair biologists make hollow arguments. But I also do think that we do share some responsibility to not turn people off completely or make them dig in harder in their positions.
Also https://xkcd.com/55/ and https://xkcd.com/128/
This is the inevitable confusion of a society that insists that nothing exists outside what we can scientifically observe, who rejects concepts of soul and love and still tries to explain their effects using only what they admit. It's like saying we bleed when we're cut because the skin must be producing that blood, denying the existence of veins or a heart.
In any case, what's specifically irritating is the entrepreneur / startuper / tech bro belief that "we can make an app to solve this", which sometimes also occurs here on HN. No, not every problem can be solved with tech or an app. Even when it can, you Random Startuper are the sidekick of the story, not the main hero who's calling the shots.
I have also met lots of very wonderful, very gay, quite-less-than-stereotypically-attractive people who could warm almost any soul with the way their smiles lit up their faces. For whatever any of that is worth.
Sex is good for your heart
A hug keeps tension away
Sex can be a stress buster
Weekly sex might help fend off illness
People who have sex feel healthier
Loving support reduces risk of angina and ulcer
Unfortunately the answers to that question trouble some people so it's difficult to establish the truth. The simple answer comes down to the fact that a species has to find a balance between maintaining genetic diversity, which is important for resilience and adaptation, and maintaining a strong breeding population. Males are there to allow some really wacky variations to exist that just wouldn't be viable in females. It only takes a tiny handful of males to take part in reproduction, but it takes essentially all females (especially considering they are only 50% of the population to begin with).
Even some of the poorest countries have very high fertility rates, as high as 6-7 births per female, so availability of women is not an issue.