What defines a, "species"?

>>7854364
>In science class we were taught that one species can't breed with another species.

That's the rule of thumb definition, but biology just isn't that neat. Because ofhow evolution works, there is no way to make a clean definition that always applies. We're all cousins.

>>7854364
It's one of those terms that was defined historically to fit ideas at the time and the definition is probably going to need to be modified.

Not being able to breed and produce viable offspring was the original definition, but we've found interbreeding between species happening again and again.

Biologists will, at some point, need to modify the definition to deal with DNA distance (Percentage of DNA difference), Significant Mutations (Distinct Changes in DNA that allow for adaptation to an environment and become prevalent in a population), and/or Allele Frequency.

The reason it won't happen is Humans. No one wants to make a definition for species that works wonderfully using some criteria listed above, and then find out it makes humans into 20 - 30 different species due to environmental isolation who have been interbreeding for ~200 years once travel became easier.

>>7854364
I'm a nicotine addict, and I am 2.8% neanderthal and 2.6% denisovan

>>7854364
By that definition all north American bears would be 1 species.

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>>7854427

>>7854375
Yeah, I thought mules were all sterile but as it turns out sometimes they are not sterile. And, they are made from 2 different species.

>>7854364
>The guardian
>A paper staffed by Oxbridge humanities graduates
>Surprised when they misuse a word

Go look at some the trash that Simon Jenkins has published.

>>7854375

>The reason it won't happen is Humans. No one wants to make a definition for species that works wonderfully using some criteria listed above, and then find out it makes humans into 20 - 30 different species due to environmental isolation who have been interbreeding for ~200 years once travel became easier.

Mmmm. MMMMMMMMM. This. So this.

If only Hitler didn't fuck shit up during the 20th century.

I like reminding myself occasionally that there is always one human alive on Earth who is more genetically similar to a chimpanzee than any other human. Always one.

Could you imagine the biodiversity drama which would occur? Interbreeding would cause a reduction in biodiversity...but inbreeding would be politically incorrect and racist.

Fucking glorious first-world drama.

4:19

4:20

>TheGuardian
Just because it has a "science" section doesn't mean they understand science. They barely understand journalism, if even.

>>7854994
It should be possible to come up with a good definition of species (and genus, and everything all the way to the top) from a combination of DNA Equality Percentage, and Allele frequency, or if necessary to add new lower level categories.

You think Polar Bears, Brown Bears, and Black Bears are separate species, what is the difference in DNA Percentage? What relative allele frequencies do they have? How are allele frequencies relative to environment?

This is possible for extant species, obviously, but DNA recovery of extinct species is becoming much easier, and DNA Cladistics for generating phylogenic trees has been around for 20 years now. The question is just getting enough DNA from different species sequenced to have enough of a sample size to generate an average.

>>7855152
>It should be possible to come up with a good definition of species (and genus, and everything all the way to the top) from a combination of DNA Equality Percentage, and Allele frequency,

A definition, sure. A good definition, not really. You'd end up with something totally arbitrary that can't possibly correspond well to functional differences.

>>7855176
>it would be arbitrary
No necessarily, statistics could be used with current clades and definitions to determine the right cutoffs. Take Carnivoria, how far from a rat is your average cat? How far apart are foxes, wolves and jaguars? Statistical study of average differences and work backwards.

>wouldn't describe functional difference
Which matters more when defining a species, phenotype or genotype? Does the fact that an Octopus eye is similar to a human eye matter in this context?

I'm of the mind to set genetic drift distances as a standard and leave functional analysis to workers.

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>>7854364

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It's pretty outdated to classify species as individuals that can reproduce and produce viable offspring. I think these days species are classified more on genetic differences and chromosomal form.