Kin Selection & Altruism

It might help to consider group size and range of protohumans. If you lived an entire lifetime in the same little (say) valley, how likely would it be to meet a person to whom you were not related to at least some degree?

Injecting genetic material into another organism looks like reproductive benefit to me (besides that, it's fun). Which is why the biological species concept cannot be meaningfully applied to prokaryotes.

What exactly is {A} other than a collection of genes which, acting together, produce the sort of phenotypic properties of which drug resistance is an instance? It seems like you are viewing {A}ness as something like a Platonic essence, with an existence independent of the existence of the individual genes of which it is comprised.

My point is that you are trying to justify altruism from the perspective of the individual organism. For the individual gene (those involved in producing resistance), such a transfer constitutes reproduction.

Altruistic behavior is defined in terms of costs and benefits, and reproductive success is the stick with which those costs and benefits are measured. I don't see horizontal gene transfer as a good example of altruistic behavior, because it doesn't appear clear whether it is a cost or a benefit, since horizontal gene transfer is reproduction.Pointing to horizontal gene transfer as altruistic behavior seems to send the discussion off into a quagmire. Reproduction, in any form, does come at a cost to the parent (I'm here to tell ya). At some point, the loss of resources due to production of additional offspring can begin to threaten the parent's reproductive success, measured not only in terms of the number of future offspring the parent might produce, but in the survival chances for those offspring, and thereby the numbers of offspring those offspring might produce as well. Therefore, reproductive success ultimately refers not to the number of children, but the number of grandchildren (hence, in environments in which resources are limited, K-selected organisms will tend to outbreed r-selected ones).

By that logic, sexual organisms do not reproduce either, since their replicating mechanisms produce a patching together of bits from two different genomes, rather than a re-creating of an entire organism. The number of copies of genes is what counts.

I agree. In fact, that you are playing word games is precisely what I hoped to point out. You seem to be locked in on the idea that "reproduction" is meaningful only at the level of complete organisms, and your view of altruism naturally follows that. From that perspective, horizontal gene transfer in procaryotes can only be viewed as something the organism is doing, and altruism -- even kin altruism -- becomes hard to explain. There are other ways of looking at this, however, beginning with viewing conjugation as something the plasmid is doing; i.e., the plasmid may be viewed as a genetic parasite.

I understand your objection. It is exactly the same as the objection I have to the narrow way you define "reproduction". What we have here (in addition to a failure to communicate) is a tempest in a teapot, and a bit of a tangent to the main topic of the thread. If it makes you feel any better, I like everything you said right up to where you presented conjugation as an example of altruistic behavior.Since you did, it seems worthwhile to take a closer look at that process, asking what it is that is behaving, and what (if anything) is being reproduced. Your position is that conjugation is 'behavior' on the part of the bacterium. I submit that plasmids are autonomously replicating entities which essentially co-opt the bacterial cellular machinery for their own purposes, and that this process of replication easily fits within the definition of "reproduction" which you have just provided. This might become clearer if you consider the fact that plasmids do not always confer an advantage upon the host; it is the plasmid that is acting -- and it is acting in its own self-interest.

The amount of material we're talking about is sufficiently negligible that its loss may be regarded as neutral. But I see that I have yet to persuade you that plasmids are best viewed as autonomous entities (examples of selfish DNA, if you will) anyway, and that they capitalize on bacterial cellular machinery to facilitate their own replication. The important thing to remember is that whether it ends up earning its keep or not, the plasmid is an uninvited guest to the cell. If you look only at those horizontal gene transfers that confer an advantage upon the recipient cell (such as antibiotic resistance) it is easy to get confused; why indeed would the donor cell want to do that? The answer, as I've tried to point out, is that it wouldn't; the proper question to ask is: what would be the advantage for the plasmid?

Good point. But I'll also point out again that not all plasmids do 'earn their keep' by offering (say) antibiotic resistance; some persist despite the fact that they may even be detrimental to the cell.A genome is a battleground.

Is extrachromosomal extragenomic?It's almost a philosophical question, isn't it?Does an exact count of the number of cells in a human body properly include commensal gut flora? Prolly a guy thing.

Yes.

I'm not sure I understand the question. Can you rephrase it?

I would say that since what constitutes an "individual organism" may not be as neat and tidy as one might suppose, the fitness of both 'guest' and 'host' need to be considered both separately and collectively.

Let me put it this way: how many genomes constitute a human genome? Is the mitochondrial genome properly regarded as part of a human genome, or as a separate 'human genome' -- and does not arriving at an answer to this question involve something closer to philosophy than to biology? It's really mostly about getting things straight in our heads, isn't it? LOL. Just testing a hypothesis.