What does it mean to be a 'human'? In
this series we are examining our definitions of being human from
several viewpoints. In Part I of this series we explored the idea
that we each have our definition of humanness and that this view
changes with time and culture.
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| Moment of conception. |
We all think we understand what sex is
and how babies are formed. Most of us however learned what we know
from our high school classes or perhaps doctors when we were expecting
children.
The details of the biology are important if we want to understand what humans are. Biology is the mechanics of our starting point to come into existence.
The details of the biology are important if we want to understand what humans are. Biology is the mechanics of our starting point to come into existence.
Definition
'Conception' is defined in the Oxford English Dictionary as “The action of conceiving a child or of a
child being conceived.” Since this is a bit of a circular definition, we can dig deeper into the dictionary to find that 'Conceiving' is the
“creation of an embryo by fertilizing an egg.”
To understand conception as a process, we first need to inspect what happens before it. We will probe sperm, eggs, and the different ways they can start the process to become human. As we will see, even the dictionary definitions used here are not accurate to the possibilities of conception.
To understand conception as a process, we first need to inspect what happens before it. We will probe sperm, eggs, and the different ways they can start the process to become human. As we will see, even the dictionary definitions used here are not accurate to the possibilities of conception.
Egg
Almost all eggs are produced inside
human female fetus while she is still in the womb. Only about a
dozen new eggs are built in the female body after this initial stage
of development. Unlike men who produce sperm cells through their lifetime, women
are born with almost all their potential children.
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| Egg cell. |
During her life time, the average woman
will release about 400 eggs though ovulation. During each month of
menstruation about 1,000 (one thousand) of the eggs die.
Eggs contain a unique half of the DNA
strands from the woman. Every egg is unique copy of part of the
woman's parents. Most eggs are generally better formed than sperm
and therefore more viable for reproduction.
Eggs by themselves can very, very rarely
conceive. More on this later.
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| Sperm cell. |
Sperm
Male human's have 'sperm factories'.
Sperm are generated starting with puberty. Thousands of sperm cells
are built with each breath taken. Barring accidents, this process
continues until the man dies.
The average man produces upwards of a 1,000,000,000,000 (1 trillion) sperm in their lifetime. The majority of sperm die by being broken down by the man's body into component parts. Sometimes sperm will automatically released as nocturnal ejections during sleep.
The average man produces upwards of a 1,000,000,000,000 (1 trillion) sperm in their lifetime. The majority of sperm die by being broken down by the man's body into component parts. Sometimes sperm will automatically released as nocturnal ejections during sleep.
Sperm contain a unique half of the DNA
strands from the man. Each sperm is a unique mixture of genetic
material from the father and mother. Like snowflakes, no two sperm
are alike.
Sperm, by itself, cannot conceive. There are some medical speculations that this is possible, but no concrete evidence of it exists yet.
Conception
There are several different ways
currently to have conception to occur:
- Sexual - by sperm and egg uniting during intercourse.
- In Vitro - where egg and sperm are united in a lab.
- Asexual - where a single egg splits to form a virgin birth.
- Cloning - inducing a stem cell to grow into a new exact copy human.
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| Sexual reproduction. |
Half of the man's genetic material from the sperm combine with and half of the woman's genetic material in the egg to start a process that leads to a new human.
Sexual reproduction is what we most often think of as conception. Sexual reproduction involves sexual intercourse.
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| In Vitro reproduction. |
This process involves taking the genetic material from the sperm and placing it into the egg in a laboratory. The egg is then allowed to divide until it becomes an ovum with eight (8) cells. The ovum is then implanted into the woman's fallopian tube.
Many eggs and sperm are united at once in the laboratory then placed into the woman often leading twins and triplet births.
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| 8 celled ovum. |
Many people have sperm or eggs extracted from their bodies for future use by In Vitro procedures allow reproduction in case of death or other personal reasons.
Ova, sperm, and eggs can be deep frozen for many years and still remain potential humans.
Asexual reproduction is when
eggs can be coaxed by nature or science into creating a human embryo
without sperm. This process is known as 'parthenogenesis' in science
and as 'virgin birth' in religion.
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| Asexual reproduction. |
Virgin birth means it is possible to
create a human without a human sperm. Plants and other animals have
been documented to have virgin births. Natural virgin births have
been claimed but there are no concrete evidence of it yet in humans
Its occurrence in humans is so rare that it is viewed by most as
miraculous.
Cloning reproduction is a
procedure where a single cell is used to create a genetic duplicate
of the organism. The cloning to-date has used the process of
transferring a nucleus from a donor adult cell to an egg that has no
nucleus. If the egg begins to divide normally it is transferred into
the uterus of a surrogate mother. There are other ways of cloning
being developed that use stem cells and do not involve an egg.
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| Dolly the cloned sheep. |
Cloning is basically a method of making a copy of an existing life form.
Famously, Dolly is a sheep that was
cloned in 1996 using early technology. Dolly's conception required
277 eggs that developed into 29 embryos of which only one survived to
become an adult sheep.
As we have observed, there are many ways for conception to happen. Our standard view of conception has been challenged in the last few decades as we learn more and more about how the process works.
In practical terms we think in terms of
sexual reproduction being how humans are made. This view has been
useful in helping us to understand how we came to be. With recent
learning and new technologies it does not seem rational to define a
human by how it is conceived. Each of the methods used ends in
building a human creature.
In our next entry, we will look at the morality of these methods and their implications on how humans
are started.
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