Reproducing animals and humans without the joint help of males and females is called Cloning. Theoretically it is possible to recreate an entire animal or human from a single cell, and that is why cloning is often called a process of carbon-copying or Xeroxing. Just as a carbon-copy is identical with the original, a clone would also be identical with the original creature.
While theoretically it is possible for scientists to think of creating an entire creature from a single cell, there are many practical barriers. Many have been experimenting with these barriers now for over a century, and finally a breakthrough has been achieved in sheep and monkeys.
The existence of natural cloning
Though cloning of mammals succeeded only in 1977, scientists received their clue to the possibility of cloning much easier from nature itself. For example, when a farmer breaks off a branch from a tree and obtains an entirely new one by planting it in the ground, it is an asexual reproduction. Thus it is a type of cloning.
There are a variety of asexual multiplication in plants and trees, and farmers and gardeners use these methods regularly and without any surprise. That is because this capacity for direct cloning has been built into these plants by the Creator himself.
In humans also a similar process takes place when twins are formed in a mother's womb. Once the sperm and the ovum merge with each other, a single cell is formed. This cell then grows and divides itself into a bi-cellular stage. Then these grow and change into a four-cellular stage, eight-celled organism, and so on. All during these stages of growth, all these cells are intimately united with each other, and are a single person -- the child to be born. However, sometimes mistakes do take place during cell division.
In rare cases, the cells not only divide themselves, but also get separated from each other. Each fragment then starts functioning as an individual human being, and grows to the full human baby from that stage. This is why some women give birth to two or more identical children. They are identical because they came into existence by the division of a single cell. They are copies of each other.
When a single cell splits up into two identical cells or more, and when each one grows independently, this is cloning. Though the sexual process produces only one life, the splitting up produces more than one person asexually. We do not marvel at this because this is a process for which God himself has given the capacity to human beings. Further, HE himself has made provisions for the safe growth of the multiple embryos. It is totally different matter, however, to mimic these in a scientific laboratory.
Reason why asexual cloning is possible
Cloning, or asexual reproduction, is possible because each cell of a living organism contains all the information that is necessary for the development and nurturing of the entire organism. Thus if somehow man is able to use the genetic information from a single cell, he can create the entire creature out of it. This information resides on the genes.
To understand this it would be helpful to look at a cell of a mammal. A living cell is a very complex factory, having (what we can call) tens of thousands of machines and hundreds of thousands of components. Out of this let us consider only two major parts: the cell and the nucleus. The nucleus contains many components, with the most important being the Chromosomes. The chromosomes carry the DNA, the carrier of genetic information. The DNA on a single human cell contain enough information to fill an entire set of the Encyclopedia Britannica (30 volumes). These DNA contain all information about how his organs are going to function, and numerous such information needed to make him a functioning living being.
Though all cells contain the same number of Chromosomes, the reproductive cells contain only half as much. Thus when a sperm and ovum unite, half of the chromosomes are contributed by each parent. Thus in each child there is a mixture of ancestral chromosomes, and this mixing process ensures that most of the harmful genetic diseases are kept in control.
Since each and every cell contains all the information necessary to create the entire creature, allowing the cell to multiply and grow should result in a mature creature from a single cell. This is the principle behind cloning. This is how a plants grow from stems cut from them. This is how a single cell, when accidentally separated into two, gives rise to identical twins. The capacity for a type of cloning is built into these organisms. But even here there are some restrictions.
To get a new plant from a stem, it has to have a certain minimum maturity. A stem lying outside this range would not grow roots and leaves in most cases. Similarly, twins are formed in humans only when certain favourable conditions are present, but not otherwise.
Difficulties in cloning
Cloning is not difficult at all in those plants and animals in which God has given them a capacity for doing so. We only have to observe certain restrictions like choosing a mature stem in the case of plants.
Cloning is more difficult, but still possible, in certain reptiles. It must be noted, however, that many of these reptiles already have the capacity for asexual reproduction. Since the capacity of asexual reproduction is built into them, this results in relative relative ease in cloning them in the laboratory. The case of mammals and humans is different.
In mammals and the humans the cells acquire specific responsibilities after crossing a threshold. This might be after the I6-cell stage, or a bit before or after that. Before reaching the threshold, which varies from organism to organism, all the cells are identical. A mature replica of the original creature can be reproduced from any of these cells at this stage. But after crossing the threshold, the cells start to specialize. It is the same original cell with all the original DNA but now one becomes a skin cell, and yet another a nerve cell.
Once a cell starts functioning as a specialized cell, it somehow turns "off" all the genetic information not needed by it. Thus even though it contains all the original genetic material, all the non-relevant information becomes dormant. Thus even if it is grown by some process, it would not be able to grow the original creature out of it. Skin cells would multiply only into skin cells, and nerves only into nerve cells -- though they actually contain all the chromosomes and all the genetic information inside them. This is the difficulty in cloning mammals from their matured cells.
In mammals and humans only their reproductive cells (sperms and ova) make all the information available that resides on their chromosomes. Thus it has been possible for scientists to perform many kinds of surgical manipulations upon sperms and ova, but the same could not be done on mature non-reproductive cells due to their specialization.
Specialization (after a certain growth) is a definite barrier kept by the Creator in all kinds of organisms. Cloning a new creature from these specialized cells has been a very difficult task because of this barrier. But now even this barrier has been overcome in some mammals, though only time will tell whether it will ultimately result in good or bad.
Bible, ethics, and cloning
Though certain kinds of cloning are already available in nature, this does not automatically justify man's attempt at cloning other organisms. The very fact that only certain types of cloning are available in nature indicates some kind of a boundary. Boundaries are indicated in Genesis when God says that living creatures should reproduce after their kind.
The need for respecting boundaries are indicated in the Scriptures where mixing of certain plants and animals are forbidden. These boundaries are also indicated through the commands that forbid humans from having sexual relationships with animals.
It must be noticed that in each of the forbidding commands above, there are no natural physical barriers. Thus multiple seeds can easily be sown together. Human-Animal sexual relationship is physically possible. God has not created any physical barriers to prevent these. But perhaps all the results would ultimately be disastrous. We do not known the full implications, but it is very clear that what has been forbidden in the Scriptures places certain moral boundaries around our actions.