The Clone Illusion - How Similar Are Genetically Identical Human Beings?

by Nicholas Graham

Cloning. A way of creating genetically identical organisms. Everyone knows that the first animal to be successfully cloned was Dolly the Sheep (Roslin Institute, Scotland, born 5th July 1996). It is a process that took, and is taking, a while to create, enhance and perfect. You would think that two genetically identical organisms, such as two humans cloned from the same DNA, would be identical, with the possible exception of physical injuries or markings acquired during a lifetime. However the level of similarity that one would initially predict is far from reality.

As genetically identical beings they should have the same physical appearance. To an extent this is the largest similarity, but that does not mean they will be exactly the same. Factors coming under the ‘nurture’ part of the ‘nature versus nurture’ argument can have a sizeable effect on the physiological aspects of a person, both internally and externally. As a result, while basically the same in appearance, it is possible for clones to appear different in clearly noticeable ways, not including and physical markings such as injuries or tattoos that could mark them as different. As well as physical appearance, genetics can also determine the way in which a person carries out physical activities, or their stamina and strength. While the environment can affect these factors, the DNA of the person will cause limits to these abilities, that cannot be overcome by environmental or external factors. Therefore, clones will always have a minimum level of similarity for physical ability and appearance, that cannot be changed naturally. 

Due to the lack of human cloning at present, there has been no possibility to carry out psychological testing to see the correlations for behaviour among clones. However clones are essentially the same as identical twins, as they both have the same genetic material. In actuality, clones are identical twins, just ones that have been created artificially as opposed to chance causing the initial zygote to split into two part before starting to change into the human embryo. As such, the results of psychological studies on identical twins should be applicable to clones as well.

There have been many psychological studies conducted on identical twins in order to determine the effects of genetics on various behaviours, from personality to intelligence. Probably the most well-known of these is Bouchard et al. 1990, also known as the Minnesota Twin Study. This study was carried out on a variety of levels of sibling: monozygotic (identical) twins raised together (MZTs), monozygotic twins raised apart (MZAs), dizygotic (non-identical) twins raised together and biological siblings raised together. They also tested individual people multiple times. The overall concordance between MZTs was 86%, one 1% less than that of the same person twice (87% concordance). This shows that genetically identical people have almost the same level of similarity in physical variables, IQ and personality as one person does when analysed twice. For MZTs, who still have the same genetic material, concordance was only 76%. This scientifically shows the effect of nature versus nurture, and the way that the environment can cause changes in genetically identical people.

Close analysis of the results of Bouchard et al. 1990 shows the way in which these differences are spread as well as the effect of the environment on certain characteristics. Environment seems to have no effect whatsoever on personality correlation between identical twins, as both MZAs and MZTs had a personality correlation of +0.49, which is a moderate correlation. However this is still lower than the personality correlation that would be achieved via testing the same person twice, showing that personality is effected by genetics, but that the same overall personality is nowhere near guaranteed.

In contrast, the IQs of identical twins have a more significant positive correlation, with 0.69 for MZAs and 0.88 for MZTs. This shows that IQ, while not entirely dependent on genetics, can be replicated through a combination of cloning and replicating the environment of the person who provided the genetic material. However it is necessary that this combination is used as 0.69 is nowhere near as strong a correlation.

Spatial ability seems to be a particular behaviour that cannot be replicated through cloning, as the study shows inconsistent correlations for both MZTs and MZAs. Memory has a similar issue, with both groups having low correlations for the twins’ memory-related ability. Therefore, cloning a human would have no guarantee of replicating either of these behaviours or traits.

In conclusion, the levels of similarity between genetically identical beings such as clones will be high in comparison to that of those who share only part of the genetic material, however some psychological and physiological aspects are heavily dependent on external or environmental factors. Some psychological aspects, such as memory and spatial ability have seemingly no reliable relation to genetics. Clones or other genetically identical individuals, cannot be guaranteed to have the same positive abilities in these aspects as the source of the genetic material. Some European and Korean companies are offering to clone your pet for you, a common example being dogs. However as I have explored in this article, while the dog may look the same there is no certainty that it will ever be able to perform the same ball-catching tricks or act in the same way as its elder clone.