Thursday, January 31, 2013

Ohhh! The Humanity (Part 2)

The Biology of Conception

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.

Moment of conception.
This entry focuses on the biology of human conception. We will survey the basic biology of what happens in conception. Using this information we will have a reference point to discuss the moral issues of what a human is resulting from religion, science, and philosophy.

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.


'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.


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.

Egg cell.
A female baby's ovaries contain about 1,000,000 (one million) eggs at birth. About two/thirds of the eggs die before menstruation begins. This leaves about 350,000 eggs in each mature woman.

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.

Sperm cell.


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.

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.


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.

Sexual reproduction.
Sexual reproduction has the union of a single sperm with a single egg creating (or conceiving) a new, unique combination of genetic material.

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.

In Vitro reproduction.
In Vitro reproduction happens when eggs and sperm are taken from humans.

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.

8 celled ovum.
Most In Vitro procedures have left over ovum which are placed in storage for future potential use.

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.
Asexual reproduction.
Asexual reproduction is when one half of the genetic material of the egg makes a mirror copy of itself to combine with. It is almost as if the egg uses its reflection in a mirror to mate with. Eggs can be coaxed into creating a human embryo without sperm. This means it is possible to create a human without conception.

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.

Dolly the cloned sheep.
The cloning process always involves using an exact copy of the DNA in the single 'parent' to start the process of creating a new organism. 

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.

Be sure to subscribe to this blog in order to follow the explorations.

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