The colour of your skin, the shape of your ears, the flexibility of your tongue and many, many more things about you are determined by your genes. Our bodies are made up of trillions of cells, and the DNA in each cell contains all the genes that make everyone different. Each gene comes in a few different varieties, or ‘alleles’. Depending on what the gene is, an allele could be either ‘earlobes attached to head’ or ‘earlobes hanging free’; or ‘tongue can roll’ or ‘tongue can’t roll’, etc. Usually every cell has two versions of each gene, one inherited from your father and one from your mother.
Scientists currently believe there are four or more genes responsible for skin colour. Presumably God gave Adam and Eve a mixture of all possible alleles for each gene – in which case, their skin was olive coloured, neither white nor black. Depending on which alleles their children inherited, they could have been white, black, or any colour in between. There are cases of olive-skinned parents having twins, one with white skin and the other with black!
The family of Noah presumably also had a mixture of all possible alleles, since everyone alive today is descended from them (1 Peter 3:20). But soon after the flood, different nations began to form. Genesis explains that these nations formed according to family clans from the three sons of Noah (Japheth, Ham and Shem).
The sons of Japheth: Gomer, Magog, Madai, Javan, Tubal, Meshech… From these the coastland peoples spread in their lands, each with his own language, by their clans, in their nations.
The sons of Ham: Cush, Egypt, Put… These are the sons of Ham, by their clans, their languages, their lands, and their nations.
To Shem also…children were born… These are the sons of Shem, by their clans, their languages, their lands, and their nations.
These are the clans of the sons of Noah, according to their genealogies, in their nations, and from these the nations spread abroad on the earth after the flood. (Genesis 10:2,5-6,20-21,31-32)
So each nation would only have the particular alleles of their ‘founding fathers’. Genesis shows Shem to have been the ancestor of the ‘Semitic’ peoples, who have mainly olive coloured skin; Japheth was the ancestor of the modern peoples of Europe, which on average have lighter skin; and Ham was the ancestor of the African peoples of Egypt and Libya (and perhaps other peoples who spread further south from there), among others. The name of Ham’s first son, Cush, means black, and a nation of Cush lived in modern-day Sudan, so it seems likely that Cush at least had dark skin. Jeremiah 13:23 refers to the distinctive Cushite skin colour (many translations call the Cushites in this verse Ethiopians).
Different kinds of dogs are even more different from each other than the different nationalities of humans! But all dogs are from the same ‘species’ just like all nationalities of people are still human, no matter what colour their skin. What’s important is that all humans, no matter what race, can come to God equally through Jesus Christ.
There is neither Jew nor Greek, there is neither slave nor free, there is no male and female, for you are all one in Christ Jesus. (Galatians 3:28)