
What's a Species, Anyway? - hunglee2
https://newrepublic.com/article/124453/whats-species-anyways?utm_medium=social&utm_source=nfrb&utm_campaign=202706
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jonchang
Well, hybridization is certainly not a new theory -- as the article mentions,
many plants hybridize quite readily, and the existence of "ring species" just
goes to show how fuzzy the biological species concept is. The proper way to
think about species is that they are _hypotheses_ to be tested, and evidence
can variously favor merging or splitting species.

In the case of conservation, there are political reasons for defining species.
The laws either have no provision for protecting populations below the species
level, or otherwise there's no political will to attempt to do so. Therefore
conservation biologists will often try to keep species "distinct" in order to
keep what would normally be termed a "population" or "subspecies" under
protection. (You might ask why bother protecting populations or subspecies
when the larger species is fine -- oftentimes there are suspected local
adaptations that would be wiped out by letting that population go extinct or
hybridize with other populations.)

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Amorymeltzer
>The search for the red wolf's origins have led scientists to a new theory
about how evolution actually works

A close reading of the (beautiful) story shows that while the red wolf
presents a nice narrative, there is little truth in this statement. It may
have caused much hand-wringing among environmentalists, hunters, and
government officials — an important conversation and issue in its own right —
but scientists remain quite unsurprised. This is just another in a long-line
of cases where "species" is hard to define. The old chestnut of "can't breed"
doesn't work in all mammals, much less bacteria where horizontal gene transfer
is common.

In terms of sequence, it's not as fun to look at, but the best example is
probably E. coli. Across all of the E. coli strains only around 40% of the
genome is shared in a "core" genome.[1] At first glance that makes no sense
and probably says just as much about our characterization of bacterial species
as it does our definition of bacterial species.

But, really, who cares? The article quotes Darwin:

>I look at the term species as one arbitrarily given for the sake of
convenience to a set of individuals closely resembling each other

Which is essentially how scientists use it now. It's very convenient for
categorization when it is, but often has no valuable meaning. You can (and
should) say the same thing about the definition of life. Are viruses alive?
It's an interesting question, but does it change anything? It's okay for some
of the edges to be a bit blurry. The fluidity of "species" is, I think, one of
the cooler aspects of modern biology. What better way to start teaching kids
about evolution and the DNA that connects us all?

1:
[http://journals.plos.org/plosgenetics/article?id=10.1371/jou...](http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1000344)

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logfromblammo
As a non-biologist, I'll just go ahead and suggest that species are defined by
a single genetic exemplar that is an actual common ancestor to _all_ extant
members of the species.

This individual then recruits additional members by hybridizing with its own
ancestor species or sibling species in the same genus. Any given organism's
species is determined by the relative genetic distance between it and the
species exemplars.

Under this regime, if we postulate a new species _Homo superior_ with, for
instance, the mutant ability to read and write text messages while also being
fully aware of its surroundings, the earliest known bearer of the mutant gene
would likely be chosen as the exemplar. If this person died and was not
preserved in any way, we might be able to reconstruct a model of their genome
via gene sequencing analyses, which would clearly show the mutant gene.

It would hybridize with _Homo sapiens_ , the parent species. Children lacking
the mutant gene would be indistinguishable from H. sapiens. Children with it
would clearly be able to trace lineage to the exemplar.

Without barriers to breeding, the new species might just invisibly replace the
parent species as a non-branching successor. In this case, we might just let
it keep the same species name, and retcon the original mutation into the
appearance of a subspecies.

The fossil record makes selection of exemplars easier, because in many cases,
only one instance even exists. Only one tooth found in Denisov cave. Only one
Taung skull found.

If there is no gene in _Canis rufus_ that is unique to a single species
exemplar, there is no unique species left. Even if it ever was its own
species, having a purely theoretical exemplar with only a few known genes,
_right now_ it is just a _lupus-latrans_ hybrid.

So for me, a species would be defined by the presence of one or more specific
genes. Those genes could be determined by sequencing DNA from actual remains,
or inferred by analysis of living members of the species.

Being able to interbreed fertile offspring seems to me to be more like a
_genus_ -level thing, because that seems pretty common in plants.

