When does life begin?

Number Nine

Necessarily, yes, because there's certainly no way to objectively define it. People, I'm convinced, don't really know what they mean when they ask "where does life begin?". They certainly never find the true answer satisfying (i.e. that the line, if it exists at all, is fuzzy because because they came from a fetus came from an embryo came from a zygote that was itself constructed from living components that were synthesized inside of a living creature which came from a fetus...).

Humans are members of the kingdom Animalia; we are, by definition, animals.

Pythagorean

I don't think you're ever going to get a satisfactory answer when you keep asking loaded questions...

bobze

.....Seriously? Are you about to argue that humans did not evolve from prior non-human ancestors and that we share these ancestors with other extant species?

If that is the case, a science forum probably isn't the place for you.

bobze

If "genetically distinct" designates personhood then many different cell lines (somatic ones) in your body that have acquired mutations throughout ones life are distinct persons.


To the OP:

Ryan has pretty much capped the thread, IMO. There isn't a hardline answer to the question of when a person becomes a person--And there never will be. Because becoming a person is a process. Its as silly as believing that turning 18 actually makes you an adult. In reality no such thing happens. Some people may mature very quickly and act like an adult very early in life, others maybe 30 and still not adults.That subjectively drawn hardline is done for the sake of social and legal purposes.

You can, as Ryan pointed out, pick many different aspects of biology to support when a person becomes a person--But all of these in the end will only weakly support that definition. Because it is a process, not an event. For instance you could take the approach of some specific milestone of neurological development. Or you could take the milestone of being able to survive outside the womb--Which again gets murky because of technological intervention. Without a NICU babies born before 24 weeks die, almost always. However, with the advent of technology at 24 weeks in high level triage centers something like 50% of babies will survive. So again, your back to ambiguity.

And any of those biological milestones all suffer the same downfall in the end: every fetus is different. No fetus is developing at exactly the same rate in exactly the same way. For example, at around 26 weeks brain waves begin to "look human"--But that doesn't mean that every fetus will reach this milestone on midnight of the 7th day of the 25th week. Or for example; reactive fetal heart tracings don't usually happen before 32 weeks, but again that isn't a hard and fast rule. I've seen fetuses at 24 weeks with reactive tracinings, conversely I've seen fetuses at 34 weeks who were non-reactive, delivered preterm for spontaneous rupture, had great apgars and were fine. Its statistics, not hard and fast rules.

Darwin123

Okay, let's. The biological issue is completely separate from the ethical issue, at least at first. However, there is more than one type of biologist. A paleontologist might look at the issue of humanity different from a psychologist. A geneticist may look at the problem differently from both.
As an amateur paleontologist, I prefer the cladastic definitions. In paleontology, an animal is considered one species throughout its entire development, from zygote to death by old age. A tadpole is still an amphibian and a frog, even though the tadpole vaguely looks like a fish.
One can not distinguish the species very well if one had only the zygote. This is a problem some paleontologists face when they have zygote fossils without any other stage. However, the paleontologist would simply look for later stages in the fossil record.
A psychologist studies the human mind. Of course, a zygote doesn't have a mind. So with regards to a psychologist, human life has to start after after the development of a brain. The psychologist may have difficulty distinguishing a human babies mind from a chimpanzees mind.
A geneticist defines the human species as a certain genome. Okay, when does an individual have a "complete" genetic set?
In some ways, the gametes have a complete genome even before fertilization. Sperms and ova have a full set of alleles. Yes, the zygote has double the chromosomes of the gamete. However, this is redundancy. Many genes are copied twice.
I could find you all sorts of biologists. Each biologist would define a different beginning to life. This is because the definition of life is operational abstraction. Biologists have to define life in terms of the tools they work with. There is no biological context separate from the instruments. The word life is relative, not absolute.
You asked what biology says. You claim not to be interested in the ethical question, just in the biological question. Here are three types of biologists. Psychologists, paleontologists, and geneticists. There are other types of biologist, but this is a good start.
Which type of biologist do you want to answer the question of when life starts?

phinds

Scientifically, no, as explained by the comments in this thread.

Politically, absoultely. Pick any definition you like and I guarantee you you can find someone who will swear to you that that particular definition is the ONLY correct one, subjectively speaking.


EDIT --- OOPS ... my dyslexia is showing again. Throughout the entirety of the statements above, the word "subjective" was translated by my feeble brain as "objective". that is, I THOUGHT they all said "objective"

skeptic2

It sounds like the answer you are looking for is that life begins at fertilization. Suppose we said that yes life begins at fertilization or no it doesn't. What difference would it make? If what somebody says about the beginning of life is different from what you believe, would it change your mind?

Does your question have anything to do with the issue of abortion and whether it should be prohibited? The answer is that it doesn't. The issue of whether abortion should be permitted is purely a political or legal one. If more people than not want abortion to be illegal, it will become illegal. So in the end the clergy or politicians can rant all they want on either side of the issue and all that matters is the law.

checkbox

I understand the classification categories refer to common ancestors (and traits) we have with other animals - Kingdom: Animalia, Phylum: Chordata, Class: Mammalia, Order: Primates, Family: Hominidae, Subfamily: Homininae, Tribe: Hominini, Genus: Homo Species: H. sapiens. There's yet more subdivisions, eg sub-phylum Vertebrata. The"missing link" that I was talking about can be asked something like "Can animal organs be transplanted into humans 100% successfully?" Look up Hyperacute Rejection, Acute Vascular Rejection, Cellular Rejection, etc

Evo

This has nothing to do with the topic, which has been answered.