Comment by sageikosa | Hacker News Reader

Comment by sageikosa | Hacker News Reader

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Also Dawkins posits a relatively good empirical definition of species boundaries (although I'm not quoting him verbatim, and I may be extending/synthesizing some of the ideas somewhat), but...a species is basically the pool of organisms available at a period of time that can generate progeny that themselves can generate progeny. That is, they have replicator compatibility...

Under that definition, humans make a species. Horses make a species, donkeys make a species, but mules do not. Apparently in the world of Star Trek, Klingons and humans make a species: Worf (Klingon) had a child with a half-human/half-Klingon woman, and Tom Paris (human) had a child with a half-human/half-Klingon woman. Not sure about Vulcans and Romulans...obviously they can mate, but I'm not sure Spock himself can have children, perhaps we'll find out in a future movie. In Futurama, Kiff reproduced with Leela.

As to the concept of a human as a "super-organism", the problem with bacteria being part of the equation is that they do not transmit their replicator payload through the germ-line transmission vector. They are not integrated into the next generation in whole or in part. Via the concept of the extended phenotype they may alter and extend their environment to improve their chance of success (and often mothers and children have the same bacteria flora), but it's better to think of it as symbiosis (or in the worst case, parasitism) than true "super-organism" reproduction. (Me thinks!)

> a species is basically the pool of organisms available at a period of time that can generate progeny that themselves can generate progeny

That's what we learned in high-school too, but as you mentioned, it doesn't make sense for donkeys, nor does it work for ring species[1], or organisms that reproduce asexually[2]. Mules can occasionally become mothers[3].

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

2. https://en.wikipedia.org/wiki/Asexual_reproduction

3. http://www.npr.org/templates/story/story.php?storyId=1226025...

I wasn't familiar with the term "Ring Species" (I've only gotten interested in evolutionary biology in the past few years), although I had considered that a "pool" might have a relatively fluctuating degrees of mutuality and incompatibility among candidate members.

Also, I hadn't considered to qualify "sexual reproduction", as asexual reproduction might be better thought of as strains (perhaps), the classification systems for simpler organisms tends to be more structural than fecund. In my defense, I tend to refer to organisms as assemblages of organs of which simpler biota can loosely be said to possess, though I always thought of the "organs" of single-cellular creatures as organelles as they are not made up of "tissue" as they are in multi-cellular organisms.

In Star Trek Enterprise a body from the future had DNA fragments from something like a dozen different "species". Vulcans, Klingon, and Human were all included.

The thing about life boundries though in biology is that the more you know the less it makes sense. All bacteria are technically a single species, as are Archaea. Virus's aren't considered alive at all, though they do evolve. Then there are asexual creatures entirely. I vaguely recall a lizard that has no real genetic diversity because they are all females that reproduce without any sex, and there are no males. So... they're not a species either, but are still reproducing. Biology is screwy.

And all navel oranges are effectively clonal (with the requisite amount of replication drift). Dawkins chief subject of study was insects, so his books are filled with descriptions (and math!) of genetic similarity and divergence within different insect colonies. Some insect species have colonies whose members have a better than (human) sibling relationship with their "sisters", and in fact may even be (1/2) clonal instances of the queen, and full clonal instances of each other. The workers themselves are non-fecund, but their genes replicate on through the fertile queen. We certainly don't want to say the sterile workers are without species, and it may make more sense to think of the insect colony as a "super-organism"...if we could get past the fact that tissues and organs are distributed, but the long term success of the genetic line is concentrated in the germ-line.

This is somewhat complicated by royal jelly. https://en.wikipedia.org/wiki/Royal_jelly

Post menopausal woman and some adult workers have both lost the ability to reproduce. But, they did have it in the past.

Which suggests the question; should we consider tribes a 'super' organism? As it includes and benefits from sterile members. What about things like monastic orders or wolf packs whose members forgo reproduction?

> Horses make a species, donkeys make a species, but mules do not.

Rarely, sometimes mules are fertile.

And as far as humans, no one's entirely sure that chimps and humans aren't inter-fertile... at least at the level of horses/donkeys.

Exception, not the rule, but I did warn it was a relatively good empirical formula, not a law of nature :-) I am of the mind that categories such as species are mental constructs to turn the phenomenal world into an approximate model-space so that understanding and action planning can be improved.

So for me rather than concepts like "species" being meaningless, they can have meaning (or at least value), but best not to think of them as iron laws. Mostly the point I was hoping to get to in my root response before I diverted myself reading my own text while typing it.

It's easier to create iron laws for categorical manipulation than it is to place observations into categories to begin with.

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