When do cells become a person?
Almost every time a sperm meets an egg, the result will NOT be the onset of a new person. In fact, in some instances, all that is produced when sperm meets eggs is cancer. It turns out that human reproduction is very inefficient. Mistakes and errors occur frequently in the process. This is a very important concept. In recent years, there has been a group of extremists on the far right who have been attempting to pass laws in the United States that would bestow on every “fertilized egg” the rights of a live born human being. From a scientific, medical, legal, religious and societal point of view – this is madness.
When does life begin?
Life on Earth began about 4-5 billion years ago. The earliest evidence for life on Earth comes from fossilized remnants of a type of bacteria called stromatolites in Greenland. This fossils have been accurately dated at about 3.7 billion years old. However, these bacteria are already quite complex. They likely evolved from more primitive life forms. A type of rock known as zircons in Western Australia contain high amounts of a form of carbon typically used in biological processes. These rocks are over 4 billion years old.
The emergence of the earliest most primitive life forms, was the start of a continuous chain that continues to grow and spread today. It is an over simplification to say that life begins at the moment of fertilization. The eggs and sperm did not appear spontaneously at that moment. A woman produces all of her eggs before she is born. A man produces his sperm continuously through life. Both eggs and sperm are living cells. It is illogical to take a single link out of the middle of a chain and say that “this is the beginning”.
It would be just as correct to say that life begins when a couple has intercourse or when they have a discussion and agree that next year they are going to try to have a baby. In the movie Back To The Future, the time traveling hero Marty McFly endangers his own existence not because he interfered with the fertilization that eventually led to him but because he interfered with his parents falling in love at a school dance.
The bottom line is that life doesn’t ever “begin” – life “continues”.
Fertilization – The scientific facts
Many people incorrectly think of fertilization as a specific event or moment. In this view, sperm meets egg and at that moment, a new person has magically formed. In fact, fertilization is a very complex phenomenon that takes place in several stages. It is impossible to define one stage as when fertilization has “happened”. During intercourse, millions of sperm enter the vagina. Only a few hundred reach the fallopian tube where fertilization occurs.
Does fertilization occur when sperm makes first contact with an egg? There are problems with this interpretation. First, the egg is surrounded by thousands of cells from the follicle called cumulus cells. An egg, or oocyte, does not exist as a solitary cell in the body. It is more accurately called a cumulus oocyte complex or COC. So when sperm make “first contact” with the egg, they are not actually contacting the egg at all – they are contacting the cells of the cumulus. Furthermore, hundreds of sperm may make contact the cumulus at the same or within seconds of each other. This clearly cannot be the beginning of a new person.
Ejaculated sperm are not ready to fertilize an egg when they enter the vagina. In response to the dilution of semen in the vagina, the levels of a protein called FPP (fertilization promoting peptide) start dropping. This results in the sperm starting to undergo several changes, which are collectively known as capacitation. During capacitation, the head of the sperm sheds some proteins and other molecules from its surface, this allows the mineral calcium enters the sperm more rapidly which results in increased energy production and then the sperm tail starts to beat more vigorously (hyperactivation). This may help the sperm power its way through the cumulus cells that surround the egg. Finally, there is a small sac of enzymes at the top of the sperm head called the acrosome. The acrosome starts to become more unstable.
Not all sperm can undergo capacitation. If these sperm contact the cumulus, nothing will happen, no person here either.
Underneath the cumulus cells, there is a hard shell of proteins that surround the egg called the zona pellucida. As the sperm approaches the zona pellucida, the contents of the acrosome are released. Acrosin is one of the enzymes that are released. Acrosin dissolves the proteins of the zona pellucida to make a passage for the sperm to get through to reach the membrane of the actual egg cell. The area in between the zona pellucida and the cell membrane of the egg is called the perivitelline space.
As you might have guessed, some sperm will fail to undergo the acrosome reaction. In fact, many sperm don’t even have an acrosome which is a known cause for infertility.
At some point, with some luck, the surface of the sperm cell will meet and fuse with the surface of the egg cell. The contents of the sperm are released into the egg cell. This includes the male chromosomes. However, “fertilization” is still not nearly complete. Membrane fusion is itself a complex and multistep process. The different stages of egg and sperm fusion are 1) the recognition and attachment of the two separate cell membranes – this is mediated by a number of sperm and egg proteins. In humans, a sperm protein called Izumo1 must find and bind to an egg protein called Juno in order for fusion to occur. The absence of either one will stop the fertilization process dead in its tracks. 2) the activation of the fusion-associated membrane. The cell membranes have two layers and are “fluid”. The membrane molecules (called lipids) will start to move around. Finally, the different layers of the egg and sperm will start mixing together forming one.
Even after the sperm fuses with the egg, there are a number of steps that have to be completed before the egg can start dividing to form the embryo. Suggesting that sperm egg fusion is “fertilization” or that this marks the beginning of a new individual reflects a basic lack of understanding as we will see in the next section.
After the sperm fuses with the surface of the egg, the egg will start a process to try to prevent multiple sperm from fusing with and penetrating the egg. This series of steps is known as the cortical reaction. Once the sperm has fused with the egg, a number of channels in the surface of the egg cell will open up and allow a large amount of calcium to enter the egg cell. This is followed by the exit of a different mineral called zinc out of the egg cell. Both of these steps (and probably more) are necessary to activate the egg cell. If these steps are blocked, then the entire process is halted – there will be no person! More enzymes are released from tiny granules just under the surface of the egg into the space between the egg surface and the zona pellucida shell. These enzymes cause chemical changes to the zona pellucida that make it much more difficult for any more sperm to get through.
Sometimes, however, more than one sperm will get through. This is one of the many instances in which an abnormal embryo forms that does not become a person but instead becomes a type of cancerous growth known as a mole or molar pregnancy.
Sorting out the chromosomes – Resumption of meiosis
The process by which sperm and eggs prepare their genetic material for further development into an embryo is called meiosis. Meiosis is necessary because while most cells have 46 chromosomes (23 pairs), normal eggs and normal sperm only have 23 chromosomes each. Meiosis reduces the number of chromosomes in the cell from 46 to 23. Yes, there are a lot of abnormal eggs that have too many or too few chromosomes. Some sperm can also have abnormalities in the number of chromosomes.
Eggs are created in a woman’s ovaries when she is a fetus inside of her mother. Is this when life begins? These eggs complete a few stages of meiosis and then stop. They stay that way for years. A few months before ovulation, if the eggs is selected to start maturing in the ovary, it will develop the ability to respond to a hormone signal from the pituitary gland, called the LH surge. The LH surge causes meiosis to inch along for a few more steps. The egg is not able complete meiosis (and get risk of the remaining extra chromosomes), until the sperm fuses with the egg membrane.
Meiosis is a stage in the process of embryo formation that results in a large number of errors. Most of these errors are lethal to the embryo. Some errors will cause the embryo to develop into a cancer. Some mistakes just stop the process outright.
Moving the chromosomes to the right spot – Pronuclear formation
Sperm are very small. The chromosomes in the sperm are packed into a very small space. The term used is “condensed”. After the sperm cell fuses with the egg cell, the condensed chromosomes are released inside the egg. The egg is filled with all kinds of proteins and molecules and fibers which are collectively referred to as the cytoplasm. The cytoplasm contains enzymes and other factors that will start to decondense the sperm. Then, a new membrane forms around the decondensed sperm chromosomes. This is now called the male pronucleus. The chromosomes from the egg will also decondense (to a lesser extent because they didn’t have to be packed into such a small space) and become enclosed by a membrane and become the female pronucleus.
In the IVF lab, embryologists can see pronuclei under the microscope. It is one of the ways in which they determine if fertilization has occurred. A normally fertilized egg will have two pronuclei. In some cases, you can see only one pronucleus or three or more pronuclei. Can you have seven pronuclei? You can! It happens – but this is NOT a person!
Inside the pronuclei, the DNA are (hopefully) starting to duplicate themselves. The pronuclei are pulled toward the center of the egg until they are very close together. The membranes of the pronuclei will then start to dissolve and the now duplicated chromosomes will start to be stretched out along the equator of the egg (you can now call the fertilized egg a zygote) . As the zygote gets ready to undergo its first division, one copy of each duplicated chromosome is (hopefully) fulled into each new “daughter” cell.
This is another of those stages that is subject to a large number of errors including lethal errors that will prevent an embryo from developing into a baby.
Starting up the genetic machinery – Recruitment of RNA
In the IVF laboratory, we can view the embryos dividing over the course of several days. One problem that can be seen to occur frequently? A dividing embryo will simply stop developing or start to fragment or degenerate. In order to develop past the first few divisions, the new embryo must be activated. Prior to this point, all these stages have been controlled by the factors that were produced by the egg before fertilization. In order to keep developing, the embryo must start turning on the genes from all of the chromosomes – those that originally came from the egg and those that came from the sperm. This process is known as embryonic activation. Sometimes it doesn’t happen.
More mistakes and dead ends
If the embryo has not accumulated too many mistakes, and does all the right things at the right time, then it may continue to the next stage of embryo development known as the blastocyst stage. The blastocyst has over a hundred cells and is filled with fluid. Remember, as all of these cells are dividing they are all forming identical cells. In some cases, the dividing embryo might split into two or three embryos. Because these cells have not yet committed themselves to becoming an arm or a pancreas, each cell can actually give rise to a whole new embryo. There is probably no greater piece of evidence that a fertilized egg is not a “person”. Because with fair frequency, a fertilized egg will become two persons! Or three persons!
At some point, late in the blastocyst stage, the cells will start to separate into cells which become the fetus (known as the inner cell mass) and the much larger group of cells which don’t become a fetus (known as the trophoblast). Frequently, the embryo will not produce any cells which become a fetus! During early pregnancy, if an ultrasound is done, the physician will see what is referred to as an empty sac. Basically, placental tissue WITHOUT a fetus!!!
Now imagine that there people who want to pass laws that give full legal status to a cell or cells or a placenta!!!
When do these cells become a person – Our religious view
A fertilized egg is not a person. Man was created in God’s image. In order to become a person, therefore, it is necessary to have a human body. The body, however, is a container, a shell to be filled with a soul. A body becomes a person when it is infused with a soul. This occur when a fetus is born and takes its first breath.
Where do souls come from?
There were two Gardens of Eden – an earthly garden and a celestial garden. In the celestial Garden of Eden, there is a Tree of Life. The Hebrew word for this tree is Etz haChayim. It is also called the Tree of Souls. When the Tree of Souls blossoms, new souls are produced which are then stored in the Chamber of Guf. The Guf is also known as the Treasury of Souls. The Hebrew word is Otzar which means treasury.
How does a soul enter the body?
When a fetus is born, a soul is brought to it by the angel Lailah. When the newborn baby takes its first breath, the soul enters the baby’s body. At this point, a complete new person is created with body and soul. It is said that sparrows can see the souls on their journey from the Guf to to the baby and this is why they have such joyous chirping. This is analogous to what is described in the Bible: “the LORD God formed man from the dust of the earth. He blew into his nostrils the breath of life, and man became a living being.”
Every baby born is important
The number of souls in the Guf is limited. According to the Talmud, the Son of David, the true messiah, will not arrive on Earth until the last soul has left the Guf. Therefore, the birth of each new child brings the world closer to the arrival of the Messiah. Thus every person who is born has value and worth.