Life - an Unequivicol Definition

And yet those who said that would not be equivocating.

I thought about this just a bit. I am having difficulty imagining how "it depends" would not be an equivocating answer. What would be an equivocating answer?

Skin cells reproduce skin cells with modifications, same with other organs, same with gut bacteria.

Is a mule's skin being alive that enough to make a mule alive? Your observation seems to be that the mules skin is alive, which is not something under question.

it means that heritable traits are passed from one generation of cells to the next, and that process maintains the ability of the mule to live

Mules do not possess inheritable traits. I think you are stretching your definition passed breaking. Mules do not evolve.

Let's take it further. Would a single cell creature with the ability to reproduce without error or mutation be alive? Such a creature could not evolve.

No. Can you show me evidence of one?

Even without being able to show evidence of such a creature, the question is enough for me to find your definition unsatisfying.

That was but one example, others would be the cells that form specific organs inside the body, each reproducing after their kind\clade ... all the elements that make up the mule are alive in this sense.

I accept that a mule is alive, the question is whether the definition you put forth works to tell me such a thing. Let me repeat your definition here:

RAZD writes: Mine is simpler: anything capable of evolution.

Mules are not capable of evolution by the accepted definition of biological evolution. A population of mules does not reproduce and accordingly there are no following generations of mules to even discuss whether there are changes in alelle frequency from generation to generation of mules. If a mule has a feature that helps it survive better than other mules, those traits cannot be passed on to any offspring to increase those traits in the population. You would have to redefine evolution somehow to make this stuff work. But you said that you were using evolution to mean biological evolution as currently understood.

What you are doing here is changing your original definition of life to talk about changes in the organs of a mule during a mules lifetime. However, said changes are not even inheritable by other mules. So yeah, the mule has living organs. But is a mule alive? Not according to your original definition.

Edited by NoNukes, : Small punctuation changes.

What about these parasites?

http://arstechnica.com/...es-harvest-atp-directly-from-hosts

Mitochondria-free parasites harvest ATP directly from hosts

quote:

---

One of the defining features of the eukaryotes is the presence of mitochondria, which burn energy-rich molecules like sugars and fats to generate the ATP that runs most cellular processes. A few rare eukaryotes, however, appear to lack mitochondria, as well as the small genome the organelles posses. The best-studied example of these organisms are the microsporidia, parasites that live in animal cells, where they cause diarrhea and bronchitis. These organisms have a mitochondrial remnant, called a mitosome, but few of the genes normally involved with its activity.

---

Crystals can reproduce without change, but are not generally considered life, so I don't see how anything that reproduces without change should be.

I did not suggest that anything that could reproduce accurately would be considered life. I am suggesting that a single celled organism capable of perfect reproduction via should not be considered not alive simply because it does not mutate.

Curiously I disagree. That their ability to reproduce is severely hampered by infertility (although not 100%) just shows they are participating in the part of evolution dealing with speciation and the formation of daughter populations that can't interbreed.

It does not show anything of the sort. What it shows is that there parents are not capable of producing viable offspring.

Again I disagree -- the following generation would have virtually zero distribution of alleles from the existing mule population, and this would be a very distinctive change in the frequency of all the alleles.

Seriously, RAZD? There is no following generation of mules. Mules do not descend from other mules.

That trait would be lost in the same way that many traits are lost through genetic drift, aka part of evolution.

Sterile animals do not undergo genetic drift.

Hiding text of duplicate post. Please see Message 63. --Admin

Edited by Admin, : Hide text of duplicate post.

Crystals can reproduce without change, but are not generally considered life, so I don't see how anything that reproduces without change should be.

I did not suggest that anything that could reproduce accurately should be considered life. I am suggesting that a single celled, biological organism capable of perfect reproduction via mitosis should not be considered to not be alive simply because it does not mutate.

Curiously I disagree. That their ability to reproduce is severely hampered by infertility (although not 100%) just shows they are participating in the part of evolution dealing with speciation and the formation of daughter populations that can't interbreed.

It does not show speciation. What it shows is that there parents are not capable of producing fertile offspring.

Again I disagree -- the following generation would have virtually zero distribution of alleles from the existing mule population, and this would be a very distinctive change in the frequency of all the alleles.

Seriously, RAZD? There is no following generation of mules. Mules do not descend from other mules. What definition are you using for 'following generation'? Certainly nothing conventional. A following generation is the offspring of a past generation.

That trait would be lost in the same way that many traits are lost through genetic drift, aka part of evolution.

Sterile animals do not undergo genetic drift. New mules do not contain random a sampling of the allelles of a current or past population of mules.

It does show speciation between horses and donkeys, one of the key elements of evolution is the division of daughter populations into separate populations that are incapable of interbreeding.

It appears that my response was not clear. I agree that speciation between horses and donkeys is complete. But what the infertility of mules does not show is that the mule offspring is on an evolutionary path. The question is whether mules are evolving and thus alive and not whether donkeys and horses are alive. I don't believe it is necessary that mules be able to evolve. They are the reproductive offspring of living creatures. That's enough. And it would be enough even if every single mule offspring were sterile.

Edited by NoNukes, : No reason given.

Edited by NoNukes, : No reason given.

Really??? I can't think how sterile individuals would not be a part of genetic drift, removing a whole genotype from the reproductive pool

I don't understand this sentence. There is no such thing as a reproductive pool of mules. Let me restate that. I can make some sense out of your statement, but it does not seem to respond to my point or to the thrust of my comment which was the following:

Mules are sterile. As best as I can tell, males are 100 percent sterile and females are essentially so. For that reason, a population of mules does not undergo genetic drift, because there is no random sampling of the characteristics of the mule population to produce a new generation of mules.

You just admitted and identified in your own words and logic that viruses and prions are less that life.

Grey area means that they are not classified as alive or not-alive. It does not mean less than alive. It may mean "undetermined", or "alive for some purposes", or "too close to call" or some other type of equivocation.

If the grey area has meaning, what is accomplished by defining the grey area away? Doing so won't eliminate whatever behavior creates the question.

Edited by NoNukes, : No reason given.

Well curiously, as regards mules in particular, I was not talking selection, I was talking death and drift as an evolutionary mechanism that stochastically removes genes. In the case of mules whole phenotypes are culled, whether their genes are beneficial or not.

Mules are a dead end. But it appears that you are willing to accept a small subset of the evolutionary process as indicating life. Nothing particularly wrong with that. On the other hand, you rely this time on death, and then drift, the latter of which I dispute occuring in mules except by death.

Which leaves for me that you are willing to say that mules are alive because they experience death. Surely that is somewhat of a tautology.

As are ALL organisms that don't reproduce. So? Is not failure to reproduce one of the processes of evolution?

At this point, I'm just trying to understand your argument. Originally it seemed to be summed up in one sentence, but I don't think our discussion since has confirmed that. It seems now that you are arguing that undergoing one or more evolutionary processes is sufficient.

Yes, mules do participate in some processes that are evolution. They are born and they die leaving their peers behind. But mules don't reproduce. Even in those cases where some female mules are fertile, they are not fertile with male mules which are invariably sterile. So there really are essentially no second generations of mules and there is no feedback from mule survival that would allow nature to produce more mules based on which mules survive. Humans have to intervene. So mules, in my opinion, fail to participate in natural selection (which I take to describe the process of surviving to reproduce and thereby pass on personal traits) and which I also take to mean that mules do not truly evolve.

It seems you keep thinking of mules as a separate population\species -- they aren't.

I respectfully disagree. Mules are a separate population and they are neither the same species as horses nor donkeys.

Edited by NoNukes, : No reason given.

Edited by NoNukes, : No reason given.

Demonstrating "capable of evolution" does not mean demonstrating every single process of evolution.

In my opinion, 'capable of evolving' ought to mean "undergoing a change in allele frequency in a population from generation to generation". But that is apparently not what you meant. We don't even agree that mules are a population, which is something I find strange. Perhaps we've reached a point where we must simply agree to disagree.

Beyond that, I think agreeing that something less than demonstrating the process of evolution is sufficient might mean that a simpler definition of life is possible.

That means hybrid and not a separate species. Mules only exist within a population of horses and donkeys that are made to interbreed,

You've skipped over something obvious. Horses and donkeys are not the same species. Therefore a mule cannot possibly be the same species as horses and donkeys. It is a hybrid. We can easily discuss a separate population of mules without requiring a separate species.

Besides that, what is a species anyway?

Separate population is not the same thing as separate species. It simply means a group of animals distinct enough to talk about. Like a population with a different number of chromosomes than either horses or donkeys.

Edited by NoNukes, : No reason given.

Edited by NoNukes, : No reason given.

Edited by NoNukes, : No reason given.

We don't say "on planet XYZ we can imagine organisms that evolve by non-genetic processes" and then accept that into the theory.

That's because a theory is not the same thing as a definition.

If you want to construct a theory about what constitutes life, that's fine. But your theory won't necessarily be a definition.

If we are searching for life on planet X, should we limit our definition of life to only things that are just like living things we find on earth? Explain why such a thing would be reasonable, because the idea seems counter intuitive.

Again, are you claiming that every new generation of mules have exactly the same distribution of alleles as the previously existing population?

I am claiming that there are no new generations of mules. I am saying that a population of mules does not produce a new generation of mules.

I thought at this point we at least understood each others arguments. Let's just end this.

Edited by NoNukes, : No reason given.