When does life begin? A scientific perspective

When does life begin?

I was driving back from a Louisville Area Skeptic‘s meetup and saw a billboard saying that a fetus has a heartbeat at 21 days.

Was that correct? More importantly, did it mean anything useful?

It’s not quite correct. Heart cells develop about 20 days after conception, and the fetal “heartbeat” is first detectable at about 22 – 23 days after conception, so 21 days is a bit early. Since pregnancy weeks (gestational age) are counted from the beginning of your last period (or 14 days before conception), we need to add two weeks to the above time-line if we are to use that framework. Let’s stick with time from conception.

Is it an actual heart?

No. It is a small amalgamation of cardiac muscle tissue. Cardiac cells beat rhythmically on their own, and in concert if they are in contact with each other. In the first week after heart cells develop (around 4 weeks post conception), they are a bulge, a tube-like formation. Between six and seven weeks after conception, the heart can pump a blood-like fluid through tubes like blood vessels.

Is that really useful in determining when life begins? Thats the wrong question altogether. The right question is “What is life?”

Life requires certain features. First of which is the capacity to reproduce, and not necessarily sexually. Your body has to replace old or damaged cells, heal wounds, grow. Second, life has to be able to carry information that can be passed on to the next generation of cells. This hereditary information is carried by cells in their DNA. Third, life has to be able to use energy to drive a metabolism. This means making proteins, burning sugars and fats or storing the same, reproducing, etc and to keep those reactions going. Finally, life must be able to respond and interact with its environment in some manner. Bacteria swim towards food, light or away from things that would kill the bacteria. Fungi grow towards food. Plants grow towards a source of light. Even quasi-alive viruses can interact with their environment as they come into contact with the appropriate molecules for their receptors to interact with. Flowing from these four functions of life is the process of evolution by natural selection.

Any one of our cells is alive, but without the whole body, they cannot meaningfully reproduce. Not into a whole new organism, not into a whole new human. You need to combine an egg cell and a sperm cell to form a fertilized egg in order to begin the process of cell division that produces a new human.

Does this mean that life begins at conception? Again, not quite. Sperm cells are alive. Egg cells are alive. Sperm cells and egg cells have all the features of life. Sperm and egg cells combined to form a fertilized egg that can divide.

Egg cells and sperm cells are alive.

Life doesn’t begin at conception, not at least, life as defined by science. Life continues.

When people ask when life begins, they are asking a metaphysical question. When does the soul enter the body?

We can’t use an instrument to detect the presence of a soul, let alone determine the moment of ensoulment. The soul is not a concept that can meaningfully be examined by science, no matter how strongly you believe in it. Until someone develops a device or test that can reliably detect a soul, science can’t consider this as a valid question.

Don’t ask a scientist if you are asking for an answer that helps you win a political or religious argument. The answer you get won’t always be the one you want.

11 comments on “When does life begin? A scientific perspective

  1. Alex says:

    I think the soul question does drive most of the religious opposition to abortion, but I still have a little trouble nailing down my own position. If I discount the soul, which I do, then what am I asking when I think about when terminating a pregnancy is acceptable or not? I’m not entirely sure. I’m largely pro-choice, but that’s a gut response, not really a reasoned position. I suppose the question comes down to when do we regard a fetus as a human child with basic human rights. We get a lot more choices of where to draw that line when we are looking at abortion than when we’re talking about successfully birthed children. The born automatically get that right to life thing. Personally, I think we could probably push that right out to 15 years old or so, but that doesn’t go over too well with the public for some reason.

  2. RIcardo Barrera says:

    “Life doesn’t begin at conception, … Life continues.”

    Exactly, that is why people who don’t understand biology should not be using it for their arguments especially those who deny evolution.

    Any biologist should be able to see that a given “individual life” really began 3 billion years ago, in an uninterrupted sequence of replication down to today.

    The question should be what is a Person? That is not a scientific question but a philosophical one. Birth was good enough for the founding fathers, anything else creates infinite problems of logic.

  3. Jason Phillips says:

    Not sure if you read replies from old posts but here I go :). I think you are missing a fundamental point. The question of abortion and life beginning have nothing to do with religion but everything to do with science. You correctly point out:

    “Egg cells and sperm cells are alive.”

    This is of course true. If you were to extract a hepatocyte from me, it would be a living cell. However you then confuse this with the fertilized egg’s status. What pro-life people are arguing (and what is scientifically demonstrable) is that what has been created is not merely a cell that is alive, but a separate and distinct human organism. No one is arguing that living cells from a human body deserve protection under the law. The idea is that human organisms deserve protection under the law.

    “When people ask when life begins, they are asking a metaphysical question. When does the soul enter the body?”

    No. The question of when a human organism comes into existence is not a metaphysical one but a biological one. I’m not trying to insult you when I say a cell biologist should know better.

    Thus, we have the synthesis of two concepts: 1.) human life (read: organisms) begin at fertilization and 2.) it is immoral kill innocent human organisms.

    “that is why people who don’t understand biology should not be using it for their arguments” -RIcardo Barrera. Agreed :)

    What do you think?

    • RIcardo Barrera says:

      I do not agree. “A separate and distinct organism” is semantics not science.

      Let me try and spell it out.

      If you take a planarian (flat worm). Cut it in half lengthwise it will re-grow both its left and right halves. Which is the original? Or have the two halves somehow become two new organisms? Which is the original? The left half which has re-grown a right half? Or is it the right half that has re-grown a left half?

      Or is it that you now have two parts that are equally the original? I say the latter.

      When an egg is fertilized genes that come from both parents which were replicated just as the genes in all cells which constitute a “person” are replicated. You would not say a liver cell vs. a muscle cell in a body are “separate and distinct organisms”.

      The embryo in fact is a continuation of both parents and is not in any way “A separate and distinct organism” genetically. It is only as the result of learning and experience separate from the parents that we can say a “separate and distinct organism” emerges.

      • Jason Phillips says:

        Thanks for the reply! Wall of text incoming :(

        With regard to the worm scenario: if you cut it in half and 2 worms emerge, is it not patently obvious that we now have 2 organisms? What was once 1 organism is now 2. This is not semantics but a scientific understanding of what an organism is. You seems to be attempting to make the point that the lines of what a living thing is can be unclear, but that is not true. No serious biologist can look at a solitary Planarridae and say that it is not a singular organism. No serious biologist can then look at the same worm after splitting and say there are not 2 organisms. Do you know what an organism is? (I know that sounds patronizing but I’m not trying to be =D)

        Let’s take you for example. Can anyone look at you and say you’re not an organism? Are you just a continuation of your
        parents and not your own individual? I think its obvious that you are, in fact, an individual that is separate from your parents (biologically speaking of course). To contend otherwise certainly strains credulity. And, to follow this train of logic, if you are an individual, when did this occur if not at conception?

        You say:
        “The embryo in fact is a continuation of both parents and is not in any way “A separate and distinct organism” genetically.”

        I’m not sure if you have a background in science but this is a false statement. Genetically, the embryo is different from both mother and father. Your genetic code today is the same as it was after you were conceived. Surely you are not contending that you have the exact same DNA as your parents? (Actually that would require you to have 92 chromosomes, since you’d need an exact copy from your father and an exact copy from your mother, but you get my point)

        You say:
        “When an egg is fertilized genes that come from both parents which were replicated just as the genes in all cells which constitute a “person” are replicated. You would not say a liver cell vs. a muscle cell in a body are “separate and distinct organisms”.”

        The first sentence here is not even a sentence (you have a prepositional phrase, a subject, a modifier, but no verb or object =[). Thus, I cannot even tell what you’re trying to say there. The second sentence regarding liver/muscle cells is EXACTLY what my first post addressed. Did you even read it =[

        Finally, you say:
        “It is only as the result of learning and experience separate from the parents that we can say a “separate and distinct organism” emerges.”

        It appears that you think cognition is imperative to being an organism. However, that classification is arbitrary does not hold to scrutiny. Is a bacteria an organism? Is a tree an organism? The answer is yes to both of these. Yet they do not think. Though the use of our brains (or lack thereof) is certainly a central feature of how humanity excels in the world, it is not definitive of this nature. Thus we can see that, with your own words, you strike the nail on the head as understanding what the issue of abortion is really about. It is not a scientific question (though you seem to be confused on this point). It is a philosophical question: what is the value of human life? And where do we get this value? I contend that such value is not a variable of function; rather it is a value that is intrinsic to the human person that cannot be taken away. Man does not get his value by what he is capable of; rather man is of infinite value simply by existing.

        What do you think?

      • RIcardo Barrera says:

        No, cognition is not necessary to being an organism. But it is the emergence of cognition that makes a “human”.

        Humanness is a subjective not a biological question.

        This changes according to social-political beliefs.

        i.e. A slave was determined to be 2/3 of a human.
        American-indians were at times argued to not be human.

        People are arguing for human rights to be extended to whales.

        The fertilized egg bears no quality that makes it human other than it’s DNA. But all of ones cells contain ones DNA. Are all our cells human organisms? They are all capable of producing individuals through cloning.

        A chimpanzee has DNA that is more than 95% identical to a human so is a chimpanzee 95% human? That is much better than a slaves 66.66%

        The definition of what is life is evolving as we get a better idea of what is possible. But it is still not settled.

        What is human is a question that is far from being understood. The human genome project mapped a particular sequence. Are we more or less human by the degree to which we deviate from that sequence? No two people are going to have identical sequences even identical twins will have different mutations.

        Miscarriages often result from mangled genetics are these human if only 95% of the DNA is uncorrupted? Suppose that only the 95% we share with chimpanzees are the uncorrupted genes, is the miscarriage both chimpanzee and human?

        Is a siamese twin one or two organisms? The use of the term organism is one of convenience. In order to understand concepts we use categories and nomenclature to make things intelligible to one and other but the naming has no effect on what it is we are naming.

        Arbitrary cut off points for the beginning of one organisms existence are just that arbitrary. The growth of a human being is like the evolution of life where one may pick an arbitrary point but on either side of the continuum there is no special moment that makes all things different.

        After 7 years or there about all cells within our body have been replaced, but we are the sum of those cells so after 7 years are we a different organism? A different person? Am I the same person today that I was yesterday? Or am I a different person?

      • RIcardo Barrera says:

        Perhaps I did not go into enough detail regarding the flat worm example.

        Yes we now have 2 worms. But the question was which is the original?

        Two new worms, really? If instead of allowing both halves to regenerate I were to immediately destroy one half after cutting the worm in two. Would you not now say that the one half that remained and regenerated the missing half was the original?

        Certainly you would not say in the case of a lizard that lost a tail and grew a new one was not the original lizard but a new one.

        Let us take monozygotic twins as an example. According to the life begins at conception “theory” when the egg was fertilized a human came into existence. Perhaps a soul was Fedex’d into the zygote. But something goes wrong with the replication process and the zygote splits into two that now grows to become two separate “organisms” which half gets the soul? Or is another soul sent to the same address? Maybe they share the soul. Half a soul, half a human? Perhaps they time share?

        A fertilized zygote can be split and split and split each split creating a new “organism.” If an organisms life began at conception then how do we end up with multiples post conception?

        It has been demonstrated that DNA belonging to one species can be introduced into the egg of another.

        What happens if we were to take human DNA and place it into the egg of a chimpanzee or gorilla and implanted that egg into the egg donor and allowed it to come to term. Is the child a human or a chimp or gorilla?

        Now suppose prior to placing it in the egg we removed the DNA we have in common and replaced it with DNA from the donor mother is it a human? The offspring would be indistinguishable from a “human.” Does the 5 or 6% difference hide the human?

        Is that where the soul resides?

  4. Leaving aside the hard sciences for a bit — If a soul is a concept of the human qualities of consciousness in intellect and emotion and/or is a term promoted by religion, then life with a soul begins at baptism (a couple of days old for Catholics; puberty-thereabouts for most Protestants). If soul is just intellect and emotion, life with soul begins when a baby thinks and feels in concert (still somewhere around infancy). If soul and spirit are synonymous, spirit just means breath, and breath needs lungs, so life begins at birth. If soul and spirit are more than breath, like some eternal or infinite concept of human consciousness quality, then soul never begins and can’t end, so it’s like a ghost or something and cannot be “aborted” in the first place.

    • Exactly, its all about cultural language and definitions, and it isn’t like those can change over time. (/sarcasm)

    • Charlie Lawrence says:

      As has been mentioned, the “soul” is a conceptual figment. I’ve tried to start with the “sense of self” but that’s somewhere around 2-1/2 to three yo. So, that can’t be the beginning. Next, I try the approach of brain waves; i.e., at what point can we measure what kind of waves? And what information does that give us. I’ve come to understand that alpha, delta and theta waves are present according to different mind states. Which of these states would a theocrat agree that life is viable or that a soul is present? Isn’t this part of the old argument that life begins somewhere around 5 mos of pregnancy? I’ve really enjoyed this discussion.

  5. I have been working on a number of biological laws that resolve the issue of when life begins.

    For example the “Law of New Life” states that all new life begins with old DNA. Of course the importance of the law lies in the fact that nothing new is brought into the new life. The DNA of the old life contains all the information that is needed to control the formation of the new life. All information that is required to form the new life is brought into the new life by the old DNA.

    And the “Law of Life” states that it is impossible to tell if a new life will live through birth. The first corollary of that law is that it is impossible to tell if the new life has enough human DNA for it to live as a human. So this law makes it clear that we cannot tell if the life is alive or human until it is born.

    And the “Law of Conception” says that most new human life dies before birth. The importance of this law is that it makes it clear that at conception there is not the creation of live, but the process of death. For example a living egg and sperm are brought into the conceptus and most often they die. It is not life at conception, but death.

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