Early humans in Africa may have interbred with an extinct species: new research

They also use string similarity algorithms to determine morphological order, so we don't strictly know the order at the most precise level.

Of course, this is all very controversial, some people think we're always changing gradually and some people think we always change rapidly. I think they're both wrong--sometimes organisms change rapidly, and sometimes they change rapidly, depending on environmental factors.

disclaimer: I'm no expert, I've just looked at it from an algorithmic view and read some taxonomical texts as I had the same question as you.

This was a definition of species for a long time. In recent years some have advocated for changing it a lot, to the point that they should just start calling different dog breeds their own species.

Or to go the other way, are dogs and wolves different species?

Is it homo neanderthalensis and homo sapiens or homo sapiens neanderthalensis and homo sapiens sapiens?

In my opinion, Denisovans and Neanderthals are both obviously types of Homo Sapiens and the argument they aren't is at this point mostly promoted by those desperately clinging to the now disproven out of africa hypothesis.

It's just a level of difference in which somebody goes, yip let's draw a line here and from anything going forwards is a new species.

Heck, it certainly isn't defined by having interchangeable blood as we all know that don't work with humans.

But when you look closely enough, there aren't really any such exact groupings in nature. Conception only involves the DNA of two individuals, not some larger group. And we know that species today have common ancestors, and it can't be that there was a precise second at which they became distinct, every split must have happened gradually.

(Like us, animals also have their own heuristics about other animals, including what sort of things they will mate with, but it's imperfect. Denim jeans cannot reproduce with poodles, as it turns out.)

As to the 6% thing that's in the the same sense that you got 50% of your genes from your mother. Most of the genes there will be identical to the ones your father has on a codon by codon basis but their origin is your mother. And by looking at the 1% of genes where humans vary from each other we can tell which genes came from this ghost population.

Apple trees mate readily with pear trees. Most citrus fruits are blends of other citrus fruits. Peppermint is a cross breed. [0]

And then there's ring species [1], whose members can each mate with similar-enough-dna members and produce offspring.

[0] https://en.wikipedia.org/wiki/Peppermint

[1] https://en.wikipedia.org/wiki/Ring_species

You can't. In practice, extinct branches of humans are classified as separate species, and animals are classified as a bunch of species because biologists get credit for discovering new species. In contrast, living branches of humans (e.g. bushmen vs. pygmies vs. everyone else) ar classified as a single species even if they have evolved largely in isolation for hundreds of thousands of years and rarely interbreed, because classifying them separately could give ammo to racists and worse.

>I'm also always intrigued by statements like this: "Interestingly, they suggest that 6%-7% of the genomes of West Africans is archaic in origin". I know it's over-simplifying for the lay-person, but 6-7% is the high end of what people claim is the genetic difference between us and chimpanzees, and we can't even reproduce with chimpanzees and don't even have the same number of chromosomes. So there's a lot more than that we have in common with some archaic species, and a lot less that we'd expect to have with closer relatives.

It usually means 6-7% of genes that vary between humans.

Those percentages aren't measuring the same thing. Chimp to human is a total genome comparison. Human to Hominid ancestor X is based on identified humane genes. The latter is a tiny subset of the former.

As others here have noted, it's generally or historically been deemed to be a pairing expected to produce a fertile offspring that can interbreed with others of the same group.

Though, really, DNA is just two RNA. We are made up of the same code that makes bacteria and even viruses. So it's bound to be messy and highly hackable.

https://www.iflscience.com/health-and-medicine/ancient-virus...

I can't readily find a really good article about the (controversial) theory that humans descended from a pig-chimp mating, but you can Google it.

We do have to discuss and reason about living creatures with other humans though, so it's helpful to name and categorize, just know that the names and categories are a human language construct, nothing more.

99% of any hominid genome - whether Neanderthal, Denisovan, or the "archaic" ancestor refererenced - is also shared with bonobos. The branching point with bonobos is at a much earlier stage of evolution, so all descendant branches have roughly the same affinity to them.

Some papers will use different definitions, and it can be confusing.

Between species (e.g. humans and chimps), it's most often considering "non-synonymous mutations," i.e. how many genetic differences there are in protein-coding genes (these are relevant to structure and function of the protein)

For distant relatives (e.g. humans and bananas), it's similar, looking specially at those genes which we can identify across many species (particularly those related to cell upkeep, DNA replication, structure, etc.).

For within-species, there are a few ways of doing it; you could model how much of the genome you expect came from each source (as this study did) (see admixture analysis, coalescence), and you could look for overall differences on the genome (of all existing variation in the species, how much is consistently different between populations) (see F-statistics for example)

https://en.wikipedia.org/wiki/Saga_of_Pliocene_Exile

Is it that human origins are rooted in chimp-pig hybridization? Probably not, but it is high on my “just might be crazy enough to be right” list. The odd similarity-dissimilarities among human, pig, and primate are just too interesting to be dismissed out of hand.

That said, classical multiregionalism is very, very dead and has been for awhile. Essentially what you're asking about has started to come up lately as a sort of in-Africa multiregionalism. This is a nightmare to model mathematically and so people just couldn't until recently when new fossils made it pretty hard to explain things any other way.

It hasn't fully emerged yet and many people don't really deal with it. Take for instance, this paper. One of the fundamental assumptions is that there was a singular set (or other time limited) of introgression events between archaic and human populations. That's a reasonable assumption in older models (and dramatically simplifies things), but it's possibly violated in an African multiregionalism model.

They claim it's not a problem because of symmetry, a point I'll admit I don't fully understand their explanation for in the supplementary material.

https://en.wikipedia.org/wiki/Silurian_hypothesis

But nevertheless, I become 2 years old every time I encounter comments like this. Thanks for the good laugh.