Something like a T-cell is, as I understand it, a living creature that our body generates. It is, of course, dependent on our body as the environment in which it can live, but they are unconnected to our nervous system and are not, unlike our gut fauna, an unrelated life form. They are, for all intents and purposes, an independent life form that we’re producing, just as (some of us) can produce babies.
Other than the T Cell and other lymphocytes, does the human body have any further progeny?
Isn’t that true of almost any of our cells? - they are alive in their own right. Admittedly some of them would not survive long outside the environment of our body, but that’s not very different from taking a fish out of water.
The same could be said of pretty much all the cells in the human body, except that most of them are physically touching other cells, but then, the blood is fairly jam-packed with cells so I expect lymphocytes are physically touching other cells (especially in you count erythrocytes - which is arguable, I suppose) much of the time. I do not really see why one should regard lymphocytes as “progeny” in any sense stronger than one could apply to any other cell.
All the cells in the body are very much dependent on the circulatory system to stay alive, and lymphocytes are certainly no exception there. That dependence, surely, (as well as the fact of being produced from, and sharing, the same DNA) is what makes all our cells part of us rather than independent organisms.
That’s what I was going to say. They’re all more or less individuals in a colony … some much more so and some much less so.
For the whole thing to work, though, they have to give up their own “goals” for the common good. That’s where apoptosis (pronounced a-puh-toe-sis) comes in. Cells commit suicide when it’s best for the organism to do so. When that mechanism (and a bunch of others) fails, the result is cancer.
Cancer is the true “independent cellular offspring” of an organism. Of course, killing the organism doesn’t work out so well for the cancer, so they’re not quite independent after all.
In “Power, Sex, and Suicide” (which is mostly about mitochondria), Nick Lane explains a lot about the peculiar circumstances that are required of a cell before it’s a good candidate to make a multicellular organism. (Number one being eukaryotic.)
Life happened shortly after conditions allowing it arose on the planet. It took 3 billion more years before multicellular life arose. Lane posits that abiogenesis (making life in the first place) is a lot easier (more likely to happen by chance) than making the transition from unicellular to multicellular-capable cells. (More specifically, from prokaryote to eukaryote, the latter having a nucleus). Fascinating book, unlike my clumsy attempt to explain it.
To anyone who didn’t follow Lemur866’s link: It’s about something called HeLa cells, cells cultured from a cancer tumor from a woman named Henrietta Lacks. Not only are they able to survive outside of a human host, they’re so good at it that they’ve become a nuisance at many laboratories: Once you’ve had a colony of HeLa cells to study, they tend to infect all of your cultures whether you want them there or not.
They’re a very interesting corner case in biology. It’s somewhat debatable whether they still count as H. sapiens: If they do, then we have an organism of species H. sapiens which survives without most of the things we think of as intrinsic to human life, and if they don’t, then they’re still the species most closely related to us, despite being almost completely unlike us above the genetic level.
One common aspect of definitions of life is that “life replicates”.
Mature T cells and other fully mature “functional” cells don’t replicate.
Your definition appears to be that the cells move around the body are a form of progeny.
Good point!