Here’s John, father of 4-year-old Jade: “I said to the teacher, ‘Yes, she’s a handful. But they’re all the same. She’s no different to the rest. They all have the same human genes.’”
Here’s Emily, mother of Lance, who’s also four: “I said to his Kindy teacher, ‘Of course Lance is different. All kids are different from each other. They have different genes.’”
Who’s right? Are kids all the same (John) or are they all different (Emily)? Here are four points to consider before picking sides:
1. Humans share more than 99 per cent of their genes. This figure explains why, in general, we look quite alike: two arms, two eyes, a nose, a digestive and visual system, and brains that look remarkably similar. We develop in much the same way, too: most of us walk at around one year of age and put two words together by about two years of age. So, one point for John.
2. The differences between us are in the details. One point for Emily. But, with so many genes in common, why would there be any differences at all?
3. Here’s one explanation for why we humans are similar and different at the same time: imagine two necklaces, both strands of green beads. The necklaces could look the same in general but there could be small differences here and there. For example, necklace A might have a bead that is slightly lighter or darker or fatter or thinner than the corresponding bead on necklace B. The beads’ differences create different necklaces: A and B.
Now imagine that necklaces A and B are human genes. A slight difference in one bead, say, its shape, can create an allele, that is, a slightly different form of a gene. Different alleles can produce genetic variations between the two children; say, Lance’s brown eyes and Jade’s black hair. There are relatively few alleles at birth, but their effects make an impact. Alleles that dominate can make us polymorphic, meaning inwardly and outwardly different looking.
Allele variations in form and function are sometimes passed on from one generation to the next. When that happens, they may result in different appearances. These observable differences are called phenotypes. An example of such a phenotype is the epicanthic fold seen in the eyelids of many people of Asian descent. Those who might believe that this is a racist observation are confused about the difference between a phenotype and a stereotype. A phenotype is a genetic phenomenon. A stereotype, on the other hand, is a subjective, widely held point of view about a group of people.
Often we might differ from one another because of differences on a single gene here and there. Yet many important characteristics that vary in degree, like height, intelligence, personality and Lance’s and Jade’s above-described behaviour, occur when a number of genes interact with each other and with the environment. For instance, a well-nourished Dutch child may have a genotype for tallness (the Dutch have a genetic propensity to be tall) and one day play basketball for the Netherlands. Yet he may have an undernourished cousin who may be phenotypically short as an adult and not make the local team. Children need good food to grow, even when they have a genotype for tallness. This fact highlights how environmental experiences can switch on and off particular genes for particular genetic traits.
4. So, while genetically speaking, humans are very similar, in particular details, we differ from each other. These differences make each of us unique.
Be that as it may, it is important to note that our common genetic outcomes and common world determine that we’re one species. While we differ from each other, we humans differ much more from other species. This is evident even when we’re compared with our closest cousins, the great apes: we’re genetically human, and they’re not.
So, who’s correct: John or Emily? The answer is: probably both. Jade and Lance are genetically similar to other kids in general, but different from other kids in their genetic details.
Dr Jennifer Smith is a Sydney-based educational, developmental and counselling psychologist.Do you have an idea for a story?
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