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Hello there, late-night blog reader from the US, or early morning bird from across the pond (sorry to everyone else!)
Earlier today I overheard -- actually, somewhat creepily eavesdropped on for several minutes -- a discussion between a few peers on the status of life through the lens of abortion. It got me thinking about it too.
Right now, for some reason I can't quite sleep, so I want to somewhat organize my thoughts on this issue in writing, because that will probably make me very tired...and I just sorta feel like it. Quite recently N. Dakota passed legislation restricting abortion rights... I'm hoping this is not the trend in other states across the country.
I think further down the line in the ongoing abortion issue -- and the N. Dakota development serves as an example -- there will come a point when the definition of LIFE will really matter for some future piece of abortion-related legislation, such as policy related to limiting abortion to before life truly begins. It seems that without a strong scientific consensus on when life starts, the definition will remain unclear and policy will struggle to form easily and reasonably around it.
So here's one idea with multiple parts...
1) This first part is incredibly tricky for me. It is perhaps partly why I really wanted to write some thoughts out. We need to start by defining "life" in the context of abortion. Those who argue against damaging embryos via abortion and other therapies due to the fact that embryos are, as they state, "alive" appeal to this concept of life. So what the hell is life? Let me begin with a skin cell. A skin cell by and large has the same genomic material as any other cell in my body, save for some neurons, blood cells, and other highly specialized cell types. It's really not much different from any one other cell in my body, if you take away the details and don't care about the function. If I pluck a skin cell off my body, and place it on some supportive growth material, thereby allowing it to thrive detached from my body, is it living? Frankly, the answer is that it is living tissue. But it is not "alive", is it -- in the sense that we can say it has a "life" the same way a human has a "life"? A cell has a life in the sense that it has a starting point and an end point. Batteries also have lives. Humans and their LIVES are different though, aren't they -- but what is the damn difference?
Even when the cell resides in my body, if I restrict my focus to this cell, it appears more appropriate to call this cell "living tissue" rather than to call it "alive". When all the cells in my body come together, I am alive. But I am still alive even without some cells. So at what point in development did I become "alive", in the sense of a human life?
Now having just typed that, and looking back on it, it still seems that this distinction between human life and "living" isn't strong. What exactly is the difference between the concept of a "human life" and the concept of living, as in, "living tissue"? In my opinion -- and please add opinions if you have any -- a human's life is distinct from "living tissue" in the sense that it is attached to some sort of consciousness. Even other animals have this consciousness too; however, whether or not this consciousness necessarily translates to intelligence is another matter, although not entirely important. The presence of a consciousness seems to serve as a good distinguishing feature when it comes to narrowing in on what life is.
2) I mentioned in the first point that whatever is special about "life" apart from the living tissue aspect seems contingent on consciousness. If we take the brain out, and hook a mass of flesh and organs up to an imaginary machine capable of keeping all the tissues alive, would this contraption be life? Science fiction seems to tell us over and over that this is not the case. In fact, when science fiction stories attempt to recapitulate life by combining machines with people or even with just machines alone, they attempt to imbue the machines with some sort of consciousness, rational ability, awareness, maybe even emotions -- stuff that needs something similar to a nervous system, or whatever the robot equivalent of that might be.
Ok, sorry about that detour. It was related though -- I think we can now shift the focus to the embryo. Let's look at development...
3) Let's step all the way back to "conception". I'll be blunt: I have a problem with being told that "life begins at conception". A simple dictionary search tells us this term describes the moment when the egg is fertilized by the sperm, causing pregnancy. Does this intricate thing called human life really begin right there, at the moment the male sex cell fuses with the female sex cell? In my opinion, at this point in the process, this fusion -- this one cell zygote where mom truly meets dad -- is still just living tissue. Why is that? By and large it's the same thing as a skin cell at this point. Same genomic material encapsulated inside. The genetic expression profiles are undoubtedly much different -- a skin cell has much different epigenetic landscape (changes to DNA and ultimately gene expression, which is how cells differentiate from one another among examples of different cell types) than a totipotent stem cell.
So it may be argued... "Well hey, you've described an all-powerful cell. That's enough difference from puny skin cells! I stand by my argument that life begins at conception -- that life begins when Mr. Totipotent Stem Cell enters the equation."
To which I am tempted to respond... Well... A skin cell is really not too much different from even a totipotent stem cell, and in time this may even be a reality (I think it likely will). Given that the cells still possess the same genetic material, it is conceivable within the world of stem cell and developmental biology that a powerful totipotent stem cell could be produced from another cell type if that cell type was exposed to certain conditions in which totipotent stem cells thrive, and if certain gene programs are activated that are also activated in real totipotent stem cells, and perhaps if other requirements are met. If skin cells have the potential to be instructed to become totipotent stem cells should I be concerned about all my skin cells, and should I be upset when I scratch myself for killing thousands of potential "lives"?
This is currently not a reality, but scientists within the nascent field of stem cell biology are getting closer and closer in similar, albeit less advanced applications. Scientists can change somatic adult cells into pluripotent stem cells (pluripotent stem cells differ from toti- inasmuch as they do not possess potential to form extra-embryonic lineages -- placenta, trophectroderm, and other non-embryonic prenatal tissues, whereas toti- do). It is not entirely inconceivable that scientists will someday unlock the capacity to form an implantable cell from another non-implantable cell type for pregnancy. As with any R&D, trials would obviously begin in small model organisms, so there is no need to fear this sort of R&D on humans.
4) So, back to the journey leading to "life"... This piece of tissue is now dividing very rapidly. Our little Mr. Totipotent has now divided into similar copies of himself. By now, many, if not all, copies of the initial cell from conception are slightly more differentiated than Mr. Toti -- they've undergone the process of becoming other types of stem cells -- soon they will become progenitors, adult cells, and other types -- only few will remain bonafide stem cells, and even these aren't TRUE stem cells in the sense of Mr. Totipotent's true stemness. So anyway, shortly after the zygote forms, cells are dividing, differentiating, and starting to form lumps that will soon segregate into distinct germ layers: endo-, medo-, and ectoderm (and some prominent figures in stem cell bio form a distinction for a 4th, the neural crest... stay tuned). These will shortly thereafter grow into primordial regions of tissue that will exaggerate into more specialized tissue types and organs.
Somewhere along the way, the nervous system happens. Consciousness and the notion of "life" in the non-living tissue sense require this nervous system development. Without it, remember, we're just dealing with a lump of cells, tissue, and ultimately a human corpse without life. So it seems to me that "when life starts" relies on when the nervous system begins to form. It turns out there is a very clear point at which the origins of the nervous system and brain begin. It's called neurulation. It's the point when cells, triggered by internal and external signalling reactions, suddenly begin to differentiate into the progenitors of the neural tube, crest, and other features that ultimately form the components of the nervous system. So any type of legislation that seeks to go further and ban abortion before there is any start to the process of neurulation might be somewhat disagreeable. I'd rather people not argue that "life begins when the sperm meets the egg". It doesn't make sense, even when justified that it "starts the natural continuum of birth" -- if I start this by implanting a skin cell turned totipotent stem cell into an organism, is that also starting the natural continuum of life? Seems reasonable to just call it "life" when the nervous system begins, or perhaps even when it is fully formed -- this would be harder to describe, though.
6) So I'm getting really tired now. This trick to get sleepy worked. About a half hour has passed! I feel like I need to conclude somehow.... Problem is, I don't think I'm finished, and at this point I can't go back and see what I need to fix. Anyway, let me know here if anyone has anything to add on this topic. I'm especially interested in thoughts on when life begins.
Edit: Just woke up and added a line or two. But still too tired to add in point 5, which apparently I was going to make, but instead made point 6 instead :S
 
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"Life"started millions of years ago.
If you think about it in terms of biological processes its no use thinking of life in terms of a single being, a single human being for example is made up of millions of individual 'lives', bacteria in our digestive system being the most obvious.
With regards to abortion I personally don't have much of a consideration for the child themselves, I am personally of the belief that not much separates a small child from any other animal except our own personal and emotional attachment so from a purely moral perspective I actually don't have much of an issue with any stage of abortion as I don't have problems with putting down animals if it cannot be taken care of or lead a good life (I am obviously not for needless slaughter).
However this is not the full picture, for me the issue lies with the Doctor concerned. I do not wish to force my own moral judgements on others, I am not a Doctor and perhaps were I presented with the issue on more real terms I would have a change of heart (we are NOT rational beings after all), I also don't have children of my own. This is why when it comes to the debate I side with my friends who are Doctors and their view on abortion is that you should be allowed to abort at a certain period to allow for serious, debilitating defects to be picked up, allowing for some time to reach the decision.
To me the debate has nothing to do with 'life' as I don't think many people consider the lives of the parents and Doctor enough, life is a difficult concept to pin down and the only reason it matters to people is an ancient books says that 'life' is sacred without truly defining it in any way that is relevant to our current understanding.
Back to your question though, you have to make assumptions to define when life starts.
If you want to make a distinction between man and animal why not start when those similarities end? Well when is that? There is nothing to suggest that a newborn human being has anything inherently special about them, we aren't born with the ability to ponder our own lives, we aren't born with a sense of individuality, there is no evidence of a soul.
What makes us human is a unique combination of our brain and vocal chords, allowing for high level reasoning and complex communication, and none of these come into play before we are born.
Life and its use in the arguments with regards to abortion are just a way for stupid people to weigh in on the debate and feel like they have an opinion. It doesn't hold up because its an impossible task to answer fully, instead we have to look for more concrete means to determine when is appropriate to terminate a life, and thankfully in most western societies it isn't an issue, at least not an issue worthy of national dialogue.
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Well, I intended to make sure to note that I'm not limiting "life" as I describe it to humans, even though I notice I use "human life" a lot. I think I noted in an earlier point that animals, too, have something about them that gives "life" in that sense more meaning than mere living tissue, or a cell's "life".
I do not think it is important to distinguish animals from human here. For the record, though, I love that topic. I can show you a couple papers that talk about that very issue -- what is different about us and animals that makes us human? Some touch on empathy.. rationality... intelligence... and more. A combination maybe. On another note, I'm confused that you say it's not an issue in the west... Abortion is an issue at least here in the US, and the topic of "life begins at conception" is raised a fair amount here. I may have misunderstood that bit of your comment though
I'll ponder the rest of what you said later on, after sleep!
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I don't really agree with argument 3.
Sure the genetic makeup of the DNA at moment of conception is like a skin cell, but unlike a skin cell it has the potential to grow into something much more and I feel that should be respected, especially if you can't be sure exactly when "life starts." Some people say 4 weeks, some people say 8 weeks, some people say when you can see the first heartbeat or the first brainwave...still others say until it actually leaves it's mothers womb, leaving open the option of partial birth abortion which honestly is grotesque. What if this living being can feel and begins to exist at the moment of conception and we simply don't realize it or mistake it for just being skin cells?
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I hear you. I guess I was thinking, a skin cell, if given the right conditions, is not absolutely barred from becoming the same sort of cell that is implanted in pregnancy, if we imagine advances in our understanding our stem cell & developmental biology. What if you endowed a skin cell with potential to differentiate into all three germ layers in addition to extra embryonic tissue? Scientists aren't inconceivably far away from that.
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Life starts at sperms and eggs. Sperms are alive. So "when does life start?" is a meaningless question.
The important question is, when is it a life form that can suffer, feel, or think?
In the beginning, it's just a cluster of cells, no more human than a straw of grass .If killing this thing is killing a human, then wearing a condom is killing a human, because what you are doing is preventing a human from being born, not killing one when it's alive.
But eventually, the embryo starts to have a brain, and nerves, and the capacity to feel pain.
This is a scientific question. I'm not a biologist, so I can't answer when that happens.
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In my opinion life starts when the baby is able to live without a connection to its mother. As in if its mother died, could it keep on living? Until it can it seems to be an extension of the mother, no independent life.
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On April 24 2013 00:25 vOdToasT wrote:
Life starts at sperms and eggs. Sperms are alive. So "when does life start?" is a meaningless question.
The important question is, when is it a life form that can suffer, feel, or think?
In the beginning, it's just a cluster of cells, no more human than a straw of grass .If killing this thing is killing a human, then wearing a condom is killing a human, because what you are doing is preventing a human from being born, not killing one when it's alive.
But eventually, the embryo starts to have a brain, and nerves, and the capacity to feel pain.
This is a scientific question. I'm not a biologist, so I can't answer when that happens.
It's not really a scientific question. When does human life "start" is more a political question than anything else. In order to make effective legislation we need to draw a line somewhere.
For legal purposes the best line to draw is birth. Life starts at birth-this solves most of the "problems" related to the legality of abortion.
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On April 23 2013 18:22 adwodon wrote:
Back to your question though, you have to make assumptions to define when life starts.
If you want to make a distinction between man and animal why not start when those similarities end? Well when is that? There is nothing to suggest that a newborn human being has anything inherently special about them, we aren't born with the ability to ponder our own lives, we aren't born with a sense of individuality, there is no evidence of a soul.
What makes us human is a unique combination of our brain and vocal chords, allowing for high level reasoning and complex communication, and none of these come into play before we are born.
Has it been proven that a baby does not ponder its own life or have a sense of individuality? Is that relevant in deciding whether it should be killed or not? High level reasoning and complex communication may not come into play even after birth. I don't think it's correct to say that one is not a human being if those capacities are yet undeveloped.
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On April 24 2013 01:37 wherebugsgo wrote:Show nested quote +On April 24 2013 00:25 vOdToasT wrote:
Life starts at sperms and eggs. Sperms are alive. So "when does life start?" is a meaningless question.
The important question is, when is it a life form that can suffer, feel, or think?
In the beginning, it's just a cluster of cells, no more human than a straw of grass .If killing this thing is killing a human, then wearing a condom is killing a human, because what you are doing is preventing a human from being born, not killing one when it's alive.
But eventually, the embryo starts to have a brain, and nerves, and the capacity to feel pain.
This is a scientific question. I'm not a biologist, so I can't answer when that happens. It's not really a scientific question. When does human life "start" is more a political question than anything else. In order to make effective legislation we need to draw a line somewhere. For legal purposes the best line to draw is birth. Life starts at birth-this solves most of the "problems" related to the legality of abortion.
When they can feel pain is a scientific question. When they have moved from the status of plant to the status of human baby
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On April 24 2013 03:14 vOdToasT wrote:Show nested quote +On April 24 2013 01:37 wherebugsgo wrote:On April 24 2013 00:25 vOdToasT wrote:
Life starts at sperms and eggs. Sperms are alive. So "when does life start?" is a meaningless question.
The important question is, when is it a life form that can suffer, feel, or think?
In the beginning, it's just a cluster of cells, no more human than a straw of grass .If killing this thing is killing a human, then wearing a condom is killing a human, because what you are doing is preventing a human from being born, not killing one when it's alive.
But eventually, the embryo starts to have a brain, and nerves, and the capacity to feel pain.
This is a scientific question. I'm not a biologist, so I can't answer when that happens. It's not really a scientific question. When does human life "start" is more a political question than anything else. In order to make effective legislation we need to draw a line somewhere. For legal purposes the best line to draw is birth. Life starts at birth-this solves most of the "problems" related to the legality of abortion. When they can feel pain is a scientific question. When they have moved from the status of plant to the status of human baby
sure, but what relevance does that have with anything?
If feeling pain were required as a threshold for legally allowing abortion, then perhaps it would be useful to use science to determine when that occurs. However, it's not and never has been.
Fundamentally the question of "when does life begin" with respect to abortion has almost always been a political question.
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Life is not a thing that can be defined as precisely as the shape of an object.
A cell is considered the smallest from in which life exists, yet DNA is the base for life, the code that allows said cell to reproduce and thus allows life to exist.
Viruses are pieces of RNA inside capsules, they occupy cells, they reproduce... are they life ? As far as I am concerned most biologists ( and medics that have nothing better to do ) still argue upon the definition of life to this day because of them.
And if RNA is life than surely the proteins it creates are life, and if those 2 are life than can even the most basic of substances be life, is H2O and Pb considered life as well ?
And what in 'life' is important to us ? To us as a person it is important what we want to be important, what we bestow our importance upon, it can be a cell, a human, an animal or an inanimate object, we can feel the same feelings for all 4.
We generally tend to hold life sacred as long as some human being feels something for said life, we tend not to give much of a crap about stray dogs but we do about owned dogs, we tend not to give much of a crap about ducks but we do if we see a mother duck with her kids and somehow relate to it and develop a bit of compassion for it's position.
But alas every farmer likes his cows and chickens, even if what he feels is only pride, and every insect might have once had a child it amused and thus the child somewhere deep inside cherishes the life of said insect yet that doesn't stop us from killing said life.
Is life thought ? And if so is a computer more alive than an animal or even a human in some way because it can think certain things in a better manner ?
I think what we consider to be the "worth" of life right now is a combination of both, the importance we bestow upon something and the thinking that something is capable of doing . In witch proportion those two combined make a life worthy enough to be let to continue ( a continuation that is alas a death of it's own, a cell right now is not the same as that same cell in 1 second... very similar but no the same; only that death is a much sudden change thus we hold it at such a lower level compared to the day to day changes to our body ) is subjective, I feel.
If someone is to bestow importance upon a fetus let them do so, people give importance to less, even to things that don't exist. The choice should be left to the individual if he wants to bestow importance upon something be it his pet, his child or a fetus, if he doesn't and that thing is not capable of enough thought to figure out what he wants to do with his own existence and give a reason to his existence than I could care less for someone having an abortion, killing his dog or abandoning a baby that they did not want.
We don't fully accept personal choice however, even if said matter doesn't concern anyone other than the person involved in making said choice, we never did as a specie accept it.
I think we should first learn to accept personal choice and personal views and maybe after we do that we as a race could be considered wise enough to actually debate what life is. We keep fighting about whether or not anal sex between 2 man will make our zen aura burn beneath the earth crust in the stew pot of an immortal beaver-goat... who are we to judge what life is and what it is worth ?
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On April 24 2013 01:37 wherebugsgo wrote:Show nested quote +On April 24 2013 00:25 vOdToasT wrote:
Life starts at sperms and eggs. Sperms are alive. So "when does life start?" is a meaningless question.
The important question is, when is it a life form that can suffer, feel, or think?
In the beginning, it's just a cluster of cells, no more human than a straw of grass .If killing this thing is killing a human, then wearing a condom is killing a human, because what you are doing is preventing a human from being born, not killing one when it's alive.
But eventually, the embryo starts to have a brain, and nerves, and the capacity to feel pain.
This is a scientific question. I'm not a biologist, so I can't answer when that happens. It's not really a scientific question. When does human life "start" is more a political question than anything else. In order to make effective legislation we need to draw a line somewhere. For legal purposes the best line to draw is birth. Life starts at birth-this solves most of the "problems" related to the legality of abortion.
I think the point is that politicians will probably want to base their understanding of what "life" is on science. So if we want to understand what the meaningful difference is between a human being and a eukaryotic cell, we're going to have to differentiate it based on the key factors we see in one organism (a fully developed human being) but not in another (the cell), and you're not going to get that understanding from a purely political perspective, arbitrarily drawing the line somewhere. So as vodtoast pointed out you'd need an understanding of what some of those factors are, what consciousness is, when people are capable of feeling pain, capable of thinking, etc.
Of course science will be involved! It would be impossible for it not to be, on such a question of what life consists of and what consciousness is. We simply aren't at the point where we can clearly establish what makes human life special, and different from killing a cattle or weeding your garden - and when that "special factor" occurs during human development. I think you're right that temporarily its a political question, because we don't have the answers and have to make a practical judgement. But long-term, this is definitely a scientific question. What politicians do with the answer is another matter, but clearly both are important and necessary in this debate.
Edit: Just as a general response, I agree with a lot of your thoughts marigold, and I think the reasonable position is somewhere in the middle. I feel like what we need to do is err on the side of caution, but not to such extremes that we consider the zygote equivalent to a human life. To be honest I feel like most of the counterarguments are religious in nature.
I think that its probably going to turn out to be a continuum, there being different levels of consciousness depending on the complexity of the brain's neural network at a given developmental stage. At one level it would be equivalent to an animal, at another a fully conscious human being. I think this issue is important, because if we can, during these early stages, identify that a child is going to be born with a serious disorder or disability (not sure if possible), we can simply abort the embryo and create another child. Perhaps its a bit grisly, but its like eating eggs. At one point its a small chick, and no one would want to eat that because its hard to kill a living being even if we effectively support it by going to the supermarket. But while they're still in egg form, its okay to cook and eat them, because there is no "life" there, in the sense of it being conscious and self-aware.
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On April 24 2013 04:34 radscorpion9 wrote:Show nested quote +On April 24 2013 01:37 wherebugsgo wrote:On April 24 2013 00:25 vOdToasT wrote:
Life starts at sperms and eggs. Sperms are alive. So "when does life start?" is a meaningless question.
The important question is, when is it a life form that can suffer, feel, or think?
In the beginning, it's just a cluster of cells, no more human than a straw of grass .If killing this thing is killing a human, then wearing a condom is killing a human, because what you are doing is preventing a human from being born, not killing one when it's alive.
But eventually, the embryo starts to have a brain, and nerves, and the capacity to feel pain.
This is a scientific question. I'm not a biologist, so I can't answer when that happens. It's not really a scientific question. When does human life "start" is more a political question than anything else. In order to make effective legislation we need to draw a line somewhere. For legal purposes the best line to draw is birth. Life starts at birth-this solves most of the "problems" related to the legality of abortion. I think the point is that politicians will probably want to base their understanding of what "life" is on science. So if we want to understand what the meaningful difference is between a human being and a eukaryotic cell, we're going to have to differentiate it based on the key factors we see in one organism (a fully developed human being) but not in another (the cell), and you're not going to get that understanding from a purely political perspective, arbitrarily drawing the line somewhere. So as vodtoast pointed out you'd need an understanding of what some of those factors are, what consciousness is, when people are capable of feeling pain, capable of thinking, etc. Of course science will be involved! It would be impossible for it not to be, on such a question of what life consists of and what consciousness is. We simply aren't at the point where we can clearly establish what makes human life special, and different from killing a cattle or weeding your garden - and when that "special factor" occurs during human development. I think you're right that temporarily its a political question, because we don't have the answers and have to make a practical judgement. But long-term, this is definitely a scientific question. What politicians do with the answer is another matter, but clearly both are important and necessary in this debate. Edit: Just as a general response, I agree with a lot of your thoughts marigold, and I think the reasonable position is somewhere in the middle. I feel like what we need to do is err on the side of caution, but not to such extremes that we consider the zygote equivalent to a human life. To be honest I feel like most of the counterarguments are religious in nature. I think that its probably going to turn out to be a continuum, there being different levels of consciousness depending on the complexity of the brain's neural network at a given developmental stage. At one level it would be equivalent to an animal, at another a fully conscious human being. I think this issue is important, because if we can, during these early stages, identify that a child is going to be born with a serious disorder or disability (not sure if possible), we can simply abort the embryo and create another child. Perhaps its a bit grisly, but its like eating eggs. At one point its a small chick, and no one would want to eat that because its hard to kill a living being even if we effectively support it by going to the supermarket. But while they're still in egg form, its okay to cook and eat them, because there is no "life" there, in the sense of it being conscious and self-aware.
Not really.
When it comes to abortion the line is going to be drawn arbitrarily. This is not a question of life or consciousness. For the majority of pregnancy, the fetus/child is not much more than a parasite. It is not capable of living without its mother.
People talk even about infanticide being acceptable in certain situations when this topic is brought up. Certainly there are scientific opinions that would agree to the notion that infanticide is not much different in its effects upon the child as abortion is to the fetus. Yet legally I'm pretty sure infanticide is not going to be acceptable any time soon.
Most of these responses are needlessly complicating an issue that isn't actually complicated in the first place. The reason it seems complicated is because of the amount of time conservative politicians have spent exacerbating a nonissue. Not that long ago (in the 60s or 70s, in fact), plenty of evangelicals in the United States supported looser abortion practices on the notion that life begins at birth.
It's not merely a scientific question simply because science doesn't really have a stake in whether politicians decide that abortion is legal at X time for Y reason. Scientists may very well say that infants don't feel things the same way adults do, but you know who is going to make the call on whether killing infants is legal? Not scientists, most definitely.
Science can be useful in informing our decision on the matter, certainly, but the question of when to draw the line for abortion isn't solely a scientific matter. It's almost wholly a public policy matter.
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Life doesn't truly begin until you sink your teeth into a delicious bite of real Chicago pizza.
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why can't life start before pregnancy?
If I choose to have a kid, but right before I jizz I change my mind.... Did I just destroy someone's future? lol
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I think that once a fetus is able to survive outside the womb, it should be considered alive. I can't recall when that typically is, but it seems reasonable to me.
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So your question is: "When does human life begin?" And what constitutes a human organism?
This is actually a good question and a really easy question to answer:
The fact that a human organism and human life begins at conception is a biological fact.
Some citations from recent textbooks:
"Human development begins at fertilization, the process during which a male gamete or sperm (spermatozoo developmentn) unites with a female gamete or oocyte (ovum) to form a single cell called a zygote. This highly specialized, totipotent cell marked the beginning of each of us as a unique individual."
"A zygote is the beginning of a new human being (i.e., an embryo)."
Keith L. Moore, The Developing Human: Clinically Oriented Embryology, 7th edition. Philadelphia, PA: Saunders, 2003. pp. 16, 2.
"Development begins with fertilization, the process by which the male gamete, the sperm, and the femal gamete, the oocyte, unite to give rise to a zygote."
T.W. Sadler, Langman's Medical Embryology, 10th edition. Philadelphia, PA: Lippincott Williams & Wilkins, 2006. p. 11.
"[The zygote], formed by the union of an oocyte and a sperm, is the beginning of a new human being."
Keith L. Moore, Before We Are Born: Essentials of Embryology, 7th edition. Philadelphia, PA: Saunders, 2008. p. 2.
"Although life is a continuous process, fertilization (which, incidentally, is not a 'moment') is a critical landmark because, under ordinary circumstances, a new genetically distinct human organism is formed when the chromosomes of the male and female pronuclei blend in the oocyte."
Ronan O'Rahilly and Fabiola Müller, Human Embryology and Teratology, 3rd edition. New York: Wiley-Liss, 2001. p. 8.
"Human embryos begin development following the fusion of definitive male and female gametes during fertilization... This moment of zygote formation may be taken as the beginning or zero time point of embryonic development."
William J. Larsen, Essentials of Human Embryology. New York: Churchill Livingstone, 1998. pp. 1, 14.
From texts and videos on embryology/prenatal development:
"Every baby begins life within the tiny globe of the mother's egg... It is beautifully translucent and fragile and it encompasses the vital links in which life is carried from one generation to the next. Within this tiny sphere great events take place. When one of the father's sperm cells, like the ones gathered here around the egg, succeeds in penetrating the egg and becomes united with it, a new life can begin."
Geraldine Lux Flanagan, Beginning Life. New York: DK, 1996. p. 13.
"Biologically speaking, human development begins at fertilization."
The Biology of Prenatal Development, National Geographic, 2006.
"The two cells gradually and gracefully become one. This is the moment of conception, when an individual's unique set of DNA is created, a human signature that never existed before and will never be repeated."
In the Womb, National Geographic, 2005.
Also, more technical and in-depth explanations:
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When the sperm penetrates the egg, the oocyte (egg) completes its second meiotic division, which results in a second polar body and a definite oocyte. The nuclei of both the mature oocyte and the sperm begin to enlarge, and become respectively the female pronucleus and the male pronucleus. Both pronuclei, which contain all the chromosomal material of the sperm or egg, replicate their DNA in anticipation of the one-celled embryo's first mitotic division, called cleavage, and the male pronucleus moves closer to the female pronucleus.
Some embryologists hold that the next stage of fertilization marks the definite moment where the zygote (new human organism) comes into being. The male and female pronucli join, and when these pronuclei come together, the 23 chromosomes from the female and the 23 chromosomes from the male unite, resulting in the formation of a zygote containing a single diploid nucleus. Embryonic development is considered to begin at this point.
Fertilization (used to describe the transformation of two parts, sperm and egg into a single entity, the human embryo, is certainly complete by the time the two sets of chromosomes have intermingled. The zygote is not genetically unique and her sex is established, both features resulting from the haploid nature of the gametes and their subsequent fusion.
However, others believe that the zygote comes to be (defining moment), when the sperm has entered and united with the oocyte. One this has happened, both sperm and oocyte undergo such significant changes that neither seems to exist in its own right anymore. The sperm breaks up upon entering the oocyte and other than its nucleus, is largely dissolved. The oocyte also undergoes fundamental changes as its zona hardens to prevent polyspermy and it completes its second meiotic division. We no longer in consequence have two distinct organic parts, sperm and egg, each with a distinct identity.
As the same time when sperm and oocyte cease to be, there now appears to be a distinct organism directing its own processes of growth and development, including the lining up of the maternal and paternal chromosomes at syngamy as well as the processes described of hardening the zona and completing the second meiotic division. The first process especially seems characteristic of a new organism, whose existence depends upon a structural barrier to outside forces, rather than a gametic cell, whose existence is fundamentally oriented towards united with another gamete and thus does not have an impermeable external barrier. For these reasons, I as well as others think it most likely that the definitive moment marking the existence of a new human organism is fertilization, defined as the union of sperm with oocyte.
It's important to be clear what is at issue here. When is there a single biological system with a developmental trajectory, or active developmental program, towards the mature stage of a human being? That's a question for which there is, in principle, a definitive scientific answer. One answer suggested is shortly after the union of sperm with oocyte. Some people believe it happens slightly later. However, there is widespread agreement among embryologists both that a new human individual comes into existence when there is a single, unified, and self-integrated biological system, and that this happens no later than syngamy.
From The Developing Human, by Keith L. Moore and T.V. N. Persaud:
Human development begins at fertilization when a male gamete or sperm (spermatozoon) unites with a female gamete or oocyte (ovum) to produce a single cell, a zygote. This highly specialized, totipotent cell marked the beginning of each of us as a unique individual. The zygote, just visible to the unaided eye as a tiny speck, contains chromosomes and genes (units of genetic information) that are derived from the mother and father. The unicellular zygote divides many times and becomes progressively transformed into a multicellular human being through cell division, migration, growth, and differentiation.
From On Static Eggs and Dynamic Embryos: A System's Perspective by Nicanor Austriaco in the National Catholic Bioethics Quarterly 2 (Winter 2002)
The egg is a cell, an embodied process in stasis that only has the life expectancy on the order of hours because it is no self-sustaining. It is unable to meet the energy demands needed for survival. In contrast, the embryo is an organism, an embodied process that has a life expectancy on the order of decades precisely because it has the capability to sustain itself as an independent entity. It is a dynamic system which arises from the necessary interactions among the mix of molecules that is created by the fusion of the egg and the sperm and it manifests itself as the visible and morphological changes which we call human development.
Sperm cells are gamete cells, which means they are not whole living organisms, and more importantly, not human (check the chromosome count), although they are a part of the whole of the male reproductive system. The embryo, unlike a sperm cell, is human; she has the genetic makeup characteristic of human beings, and most importantly, the embryo is a complete and whole organism and individual human being, though immature. The human embryo is fully programmed and has the active disposition to use that information to develop herself to the mature stage of a human being, and unless prevented by disease or violence, will actually do so, despite possibly significant variation in environment (in the mother's womb, in vitro).
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Heh, thanks TerribleTrio. Unfortunately I think you may have misunderstood where I was going. What you are getting at is an issue of simple semantics, which was why you misunderstood the question as being basic and simple to answer -- of course it's my own fault for not being clear enough! Yes, we may call it "life" based on simple definitions, but at that point the zygote is not "alive" in the same sense a human is alive -- rather it's alive like an isolated skin cell is alive (which shares the exact same genetic material as the zygote embryo). Genetically it is very much the same as any other one cell descended from it later in development. There actually is little difference between cells on a single cell level within an organism. Gene expression programs and epigenetic profiles are very different, but core genomic content is conserved. The single totipotent stem cell that ends up giving rise to the living human in vivo could conceivably be initiated in vitro from another cell type provided greater understanding in stem cell and developmental biology -- I would not want to call this derived totipotent stem cell at that stage a human, though. What I was getting at was cutting into the technical definitions from developmental neuroscience and more importantly bioethics perspectives. Thanks for the basic biology definitions though -- that's quite a list in any case! By your post history I can now see that you're a decidedly hardcore pro-lifer -- one that argues all forms of abortion are immoral, even abortions right after conception, tsk tsk. As such I'm sure it was that you already had this list at the ready, and assumed this thread was a basic "when does life begin" and not a more in depth look at it, whereby the basic definitions you provided just now are already clearly understood, acknowledged, and moved beyond. I was hoping to discuss what's beyond those basic definitions, hehe. Thanks anyway
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This sort of debate is quite odd sometimes in our legal system as well. My mind always explodes when I hear of a case of a pregnant mother being killed and the defendant is charged with 2 counts of murder.
How is it murder when criminal billy bob kills the mother but when the mother doesn't "want" the baby it's just a standard abortion? Literally makes no sense to me sometimes. How can you draw a line arbitrarily here and expect to make any sense. I wish real life were so easy where you can just draw lines how you want them to fit in for you.
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EPT
