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Comment by joshbaptiste | Hacker News Reader

I live in a world where 90% of my friends and family believe that they came from the sins of a woman who decided to eat an apple. I recently read a book called Sapiens, this book really drilled into my mind that we homo-sapiens are a derivative of a single great ape that had two daughters, one that became the ancestor of all chimpanzees and the other all humans.

If human origin interests you there is a great 10 minute video from the Youtube Kurzgesagt channel that lead me to read Sapiens.

https://www.youtube.com/watch?v=dGiQaabX3_o

https://www.amazon.com/Sapiens-Humankind-Yuval-Noah-Harari/d...

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Minor derailing: it's not necessarily accurate or useful to think about speciation as "one parent with two divergent children". It's usually more about populations with fuzzy boundaries.

Speciation events tend to look more like, imagine you take a town of two thousand people and send half of them to the moon for a million years. The moon men and the earth men would evolve into two different species; if you looked really hard, you could find a single common ancestor from whom everyone in that town descended, but it's not like one of his children went to the moon and one stayed on earth; some of his great-great-*-grandchildren went to the moon and some stayed on earth. The common ancestor was hundreds or thousands of years before the population split in two.

Moreover, breaks don't always happen cleanly. Imagine for the first ten or hundred thousand years someone from earth would occasionally migrate to the moon or a moon man would return to earth. The same thing would have happened with proto-humans and proto-chimpanzees: long after the two species had begun to diverge they would still be interfertile, and some mating (or "gene transfer", if you prefer) would still happen long past the point you'd begin calling them two different species. Eventually the two species would stop being mutually fertile or even attractive and the rift would be complete, but look at how many big cat and horse-like species can still occasionally pull it off.

Evolution is messy, and the bush of life is complicated.

Yeah, but it's still interesting that there exists an "Eve" connecting any two entirely different organisms.

Not really. There's a hundred of them. A whole bunch of candidates that are at the borderline and are ancestors of every member of the species.

As an extension of that fact, if there was a single true Eve the population would be at extremely high risk for genetic defects.

It's called a population bottleneck, where a near extinction event forces almost all individuals to share a large proportion of their genetic material, and the most recognizable example is in cheetahs.

http://cheetah.org/about-the-cheetah/genetic-diversity/

Nope. Any two organisms have a unique MCRA of either gender. https://en.m.wikipedia.org/wiki/Mitochondrial_Eve

Mitochondrial Eve is the most recent common ancestor of our mitochondria. But that only tracks purely mother-to-mother descent; there could be a more recent female common ancestor.

Consider the hypothetical population consisting of two people, whose fathers were both first cousins and whose mothers are second cousins, on their mother's... side.

Their mitochondrial MRCA is their great-great-grandmother on their mother's side, but their MRCA's are their great-grandmother (and great-grandfather) on their father's side.

The entire human family tree is like that, but way, way more complicated.

That is a very specific thing.

It only applies to mitochondria, not the genes in the nucleus or anything constructed from those genes.

It's only unique because the "MR" in MRCA stands for "most recent".

You could have a species that's a million years old with an MRCA that's only 500 years old. You could also have a species with no MRCA. (As in, the only way to find an MRCA is to trace back into ancestor species.) Picture two islands where only males travel between them.

USA is a strange place.

My dad was a geneticist at Harvard and we lived across the street from Stephen J. Gould. When people on Facebook are having a conversation about how Benghazi is a sign of the second coming of Christ, I sometimes take a moment and question my own beliefs. The foundation of my beliefs isn't because someone said punctuated equilibrium is a thing but that tests can replicated and peer review scientific research can stand the test of time.

I don't think peer review is one of the foundational ingredients. Scientific work should be repeatable and falsifiable, IMO that is all that really matters. These two properties are already hard to muster though.

In centuries past, with small experiments, "peer review" actually was replication—your peers would go and do the experiment themselves and confirm your finding.

Insofar as experiments are now too large and costly to allow for "I'll just go check that in my lab tonight"-type replication, peer review is increasingly just a status game.

The most valuable thing about peer-reviewed journals isn't that a handful of chumps proof-read the articles before publication but that the journals are widely circulated and read by the appropriate set of scientists and technicians. One of two things will happen after publication.

The paper will have no impact, no one will base any further work on it, no one will cite it, and it will vanish like a fart in the wind. In this case, the author gets minimal prestige, and can claim a publication in a maybe-prestigious journal with an embarrassingly small number of follow-up citations. No fame, money, or power for the author, and no impact (negative or positive, if the paper was right or wrong) on the world.

Or the paper can spark a lot of ideas in the people who read it. They'll try to build on it, or they'll try to use a technique from it in another application. When this happens, if the paper was solid, then the original author gets citations, speaking engagements, money and power. If the paper was less than solid, and the people trying to build on it keep having trouble, that is when the original author's house of cards comes crashing down.

You don't need to directly replicate an experiment when you can build on it. If your experiments building on the original experiment make sense and give consistent results, you've just validated the original research in another way. If your experiments don't, and after weeks and months of wasting time checking your own work and making sure you're not doing wrong, you slowly reach the conclusion that the original research was bogus, then you begin to get angry. Then you begin to tear into the original author and his research, publicly denounce him for wasting your and everyone else's time. Then science self-corrects.

So science is generally OK -- either bogus research that gets published has no impact (no different that a lot of good research :-P ), or it proves false when other people try to build on it.

Who gets into trouble, is science journalists and laypeople who read newly published articles and assume they are gospel.

You're talking about the kind of sciences with applied-science subfields, where experiments form a natural hierarchy with new knowledge necessarily building upon old.

Fields like psychology, on the other hand, need replications—"assuming another result as axiomatic in your own experiment" just doesn't come up much.

Why do you think researchers in the various subfields of psychology do not build on each others' work? What do you think they are doing when they read each others' papers and cite them?

Peer review as currently done certainly isn't foundational to the scientific method, but the general principle of having ideas checked and examined by as many other minds as are capable of understanding them, does lead to stronger and more reliable ideas over time. Not everything that science deals with is quantifiable or directly testable; results must be interpreted, and theories have to be made about the wider reasons for those results in order to come up with the next set of experiments; this is the realm of discussion and argument, rather than measurement or direct tests, and science is best advanced when there is strong, productive discussion among competent arguers.

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