Mitochondria have their own DNA, which is separate from the DNA found in the nucleus of the cell. And both organelles use their DNA to produce many proteins and enzymes required for their function.

Because of recombination, siblings only share about 50 percent of the same DNA, on average, Dennis says. So while biological siblings have the same family tree, their genetic code might be different in at least one of the areas looked at in a given test. That’s true even for fraternal twins.

Identical twins are the only siblings that share 100% of their DNA. Non-identical brothers and sisters share about 50% of inherited gene variants, which is why siblings and fraternal twins can be so different.

Of the trillions of cells that compose our body, from neurons that relay signals throughout the brain to immune cells that help defend our bodies from constant external assault, almost every one contains the same 3 billion DNA base pairs that make up the human genome – the entirety of our genetic material.

Humans share 99.9% of our DNA with each other. That means that only 0.1% of your DNA is different from a complete stranger! However, when people are closely related, they share even more of their DNA with each other than the 99.9%. For example, identical twins share all of their DNA with each other.

Does everybody have the same genome? The human genome is mostly the same in all people. But there are variations across the genome. This genetic variation accounts for about 0.001 percent of each person’s DNA and contributes to differences in appearance and health.

Human DNA is 99.9% identical from person to person. Although 0.1% difference doesn’t sound like a lot, it actually represents millions of different locations within the genome where variation can occur, equating to a breathtakingly large number of potentially unique DNA sequences.

Your genome is inherited from your parents, half from your mother and half from your father. The gametes are formed during a process called meiosis. Like your genome, each gamete is unique, which explains why siblings from the same parents do not look the same.

On the biggest steps in early human evolution scientists are in agreement. The first human ancestors appeared between five million and seven million years ago, probably when some apelike creatures in Africa began to walk habitually on two legs.

Artists invented the first pigments—a combination of soil, animal fat, burnt charcoal, and chalk—as early as 40,000 years ago, creating a basic palette of five colors: red, yellow, brown, black, and white.

The two genes most relevant to lighter skin colour in Europe originated in the Middle East and the Caucasus about 22,000 to 28,000 years ago, and were present in Anatolia by 8,500 years ago, where their carriers became associated with the Neolithic Revolution.

Because the Neanderthals had lived in Europe for several hundred thousand years, it was reasoned that natural selection gave them light skin and hair colour helping to prevent diseases like rickets from occurring.

Natives of Buka and Bougainville at the northern Solomon Islands in Melanesia and the Chopi people of Mozambique in the southeast coast of Africa have darker skin than other surrounding populations. (The native people of Bougainville, Papua New Guinea, have some of the darkest skin pigmentation in the world.)

The dominant form codes for a “dose” of dark skin and the recessive form codes for a “dose” of light skin. The darkest skin is due to six dominant “doses” and the lightest skin is due to six recessive “doses”. Varying combinations of the alleles result in seven discrete colors.