While it's not the only factor that helps determine who we are, genetics has a crucial influence on our appearance and our psychology. It is not only the color of the eyes, hair or skin inherited, but personality traits such as extraversion and emotional stability depend, to a large extent, on the genes transmitted to us by our parents.
In this article, we will help you answer questions that you surely asked yourself, especially if you are pregnant: what will my baby look like? Who will he/she look like, both physically and mentally? For this purpose, we mention 6 keys that can help you to get an approximate idea, although genetic inheritance has an important degree of randomness.
It isn't possible to predict definitively what our future baby will be like; however, we can deduce some clues from our own physical and personality traits, from those of the other parent and close relatives of both.
Let's look at how aspects such as skin, hair or eye color, height, weight, personality, and intelligence are inherited. It is essential to take into account, in addition to the relative randomness of transmission and genetic expression, the important influence of environmental factors, especially in the case of psychological traits.
Before starting to talk about the genetic inheritance of physical traits, it is important to talk about the dominant and recessive alleles in which the genes manifest themselves. In a summarized and simplified way, we can say that each allele, or form of expression of a gene, can be dominant or recessive concerning others. Most traits depend on sets of genes, not just one.
So, for example, in the case of skin color, the studies indicate that dark tones are expressed as a priority in relation to lighter ones. In consequence, there is a higher probability that the skin of a baby of someone with dark skin and another one with lighter skin will tend to look like the skin of the first parent, and the genes of the second parent will reduce the intensity of the pigmentation.
Dark hair tones are dominant with respect to the lighter ones; so, the probability that the baby has brown hair if one of the parents has it brown is very high. Blond and ginger hair are considered recessive traits and, although they can appear many generations later, it is quite common for the children to have brown hair even if the parents have it a lighter color.
As happens with the hair and the skin, dark colored eyes depend on very dominant alleles. Green and blue eyes, which are closely related, are reproduced in children as long as they are present in both parents; on the contrary, if one of the parents has dark colored eyes and the other one has them a lighter color, the baby is likely to have them dark.
Some other specific physical characteristics are dominant, so it is highly probable that they are expressed in the baby even though they are only present in one of the parents. Among these, we find freckles, dimples, hairline, big nose, long eyelashes, thick lips, and the earlobes attached to the face.
To answer the question: what will my kids be like? We have to talk about personality traits.
We can define personality as a relatively stable pattern of behavior, cognition, and emotion. Its development is influenced by biological and hereditary factors as well as by other socio-cultural factors; in this sense, we can distinguish between temperament (the cerebral, physiological and hormonal basis of personality) and character, which is developed by the interaction with the environment.
About the temperament, it is important to highlight the importance of genetic inheritance in some personality traits, in particular, in the degree of emotional stability and extraversion: genetic studies suggest that inheritance explains between 40% and 60% of the interindividual differences in these dimensions (Tellegen et al., 1988).
Intelligence is a complex concept, whose meaning varies a lot among individuals; for example, while many people consider that emotional intelligence is as relevant as spatial and mathematical intelligence, others ignore it and believe that the term has a more limited meaning and tends to the rational and numerical. In addition, the famous intelligence tests are questioned by many experts in psychology.
As happens with personality, it is believed that more or less half of the variability in intelligence depends on genetic inheritance, understood from a numerical point of view through the concept of intelligence quotient (IQ). This influence is more evident in the case of fluid intelligence (reasoning and resolution of new problems) than in the crystallized one (knowledge accumulated throughout a lifetime).
Tellegen, A., Lykken, D. T., Bouchard Jr, T. J., Wilcox, K. J., Segal, N. L.& Rich, S (1988). Personality similarity in twins reared apart and together. Journal of Personality and Social Psychology, 54(6): 1031–9