As a scientist then, how do you define life?
I would define something as alive if it’s undergoing basic metabolic processes and if it’s either directly (like a bacterium or sperm cell) or indirectly (like a kidney cell or leaf) contributing to an organism’s ability to reproduce.
Unfortunately, that is not a very useful definition in terms of deciding when human life begins, because it says nothing about the value of a particular type of life. By that definition, a bacteria or a sperm cell is equal to a fetus, yet our society emphatically does not see them as the same. The value aspect is why this is a societal question, not a scientific one.
If we encounter such activity as you describe “going on in an embryo or fetus” on another planet, would science not call it life?
But if you as a scientist enounter such metabolic processes outside of Earth on another planet, you consider it life, but not here on Earth?
The scientific/biological definition of life is generally something along the lines of “made up of cells, capable of converting raw materials into energy, capable of at least cellular reproduction, DNA present.”. With maybe a few other requirements - debates center around whether things like viruses (not made up of cells, per se) are alive. This is irrelevant to the abortion debate, which isn’t trying to define “life” so much as “person,” although there’s great benefit to one side to confuse the two.
Note that this differs from the medical definition, too. By the biological definition, the brain dead patient is still alive, but by the medical definition, they aren’t. As smeghead said so succinctly, it depends on the definition you want to use.
Of course, 80% of all GD questions basically boil down to “words do not have precise definitions most of the time.”
I would say that scientists are having a difficult time defining life, but not at this end of the spectrum. The difficult cases are more along the lines of “are viruses alive”, or when to define a dying cell as dead. Most scientists would agree that cells that are engaged in natural cellular processes are alive, and that organisms made up of many such cells are also alive. So certainly anything that has a beating heart is alive, and exists much earlier than that.
As far as human, one can define human as having human DNA. There may be a little fuzzyness around the edges, but for the purposes of this argument a pregnant woman’s fetus would fall into this category.
Where it gets tricky is what you do with this information. From the definitions I used above, fingernail clippings are at least temporarily alive, as is a sperm or blood sample. Human tumor samples can be kept alive decades after the original host is dead. So using this definition of life to inform the abortion debate is rather useless unless you want to carefully preserve and give rights to every blood sample.
ok, sure. A beating heart is a sign of life. Now what?
Again you are misunderstanding what “life” means to a biologist. It has nothing to do with self awareness, or the morality of “killing” it.
A bacteria is alive, a plant is alive, a slime mold is alive.
Scientists probably would (as well as throw a huge office party when we find the first signs of “living” extra-terrestrial life).
But that doesn’t mean that such life automatically gets the same protection(s) under the law (U.S.) as a human does. And that is a subjective and legislative, not scientific, process.
An embroy or a fetus is clearly alive, since it is made up of living cells. Similarly, we could take a living cell from your skin tissue, and that cell would be alive. But even though it is a living human cell, that doesn’t make the skin cell a living human being.
I’m not interested in whether it gets protection or not. I’m interested only in what science would factually define it as. It wouldn’t bother me if after they determined it to be life on Pluto, they then incinerated it. If the behavior they witness on Pluto and define as life on Pluto is the same as behavior they witness here on Earth, why can’t science definitively say the same being is life here on Earth?
By a simple biological definition, every step along the way from sperm and egg to adult human is undeniably alive. At no point does a living human emerge from nonliving parts. There is no question about that.
They can, a fetus is alive, a sperm cell is alive, an unfertilized egg is alive, the bacteria in your gut is alive. A heart beat has nothing to do with it, other than being convenient (but rather inaccurate by modern standards) method, historically, for doctors to determine when a mammal has gone from being alive, to being dead.
Thank you. A beating heart in a human is a sign of life in that human.
Reread what was posted - that’s only true sometimes. Depending on how the observer is defining “life.” A human can be alive without a heartbeat, or not alive with one, by the varying definitions.
At a cellular level. A heart cannot beat unless the heart cells are alive. It tells us absolutely nothing about, say, brain activity.
Possibly because science has no way of detecting brain activity at that point? True?
At what point? Science can detect brain activity at many points of human life. I think many of the people in a persistent vegetative state have a beating heart, and science can determine whether or not there is brain activity.
What do you mean by brain activity? We can look for, again, basic metabolism going on, or we can look for neuronal activity - the propagation of electrical signals and whatnot.
Simply, a beating heart is evidence that (a) the heart itself is alive and (b) it’s receiving the signal(s) it requires to beat. It tells us nothing beyond that. Similarly, whatever brain activity you’re talking about simply tells us that that brain is alive and functioning sufficiently to perform that activity, and nothing else.
Look, I get the distinct sense that you’re attempting to oversimplify a complex problem, presumably with the goal of scoring points in some sort of debate. If you would give some context or some idea of where you’re trying to go with this, this would be much easier. Are we talking about abortion? Persistent vegetative states? Alien life forms? What?
As is breathing (and that too has historically been used to detect when someone died, by placing a mirror in front of the mouth). By that standard of measurement, no a fetus is not alive.