Question

3. Read the following paragraph from the Smithsonian Institution website “What does it mean to be human?” “Researchers compared the Neanderthal mtDNA to modern human and chimpanzee sequences and found that the Neanderthal mtDNA sequences were substantially different from both. Most human sequences differ from each other by an average of 8.0 substitutions, while the human and chimpanzee sequences differ by about 55.0 substitutions. The Neanderthal and modern human sequences differed by approximately 27.2 substitutions. Using this mtDNA information, the last common ancestor of Neanderthals and modern humans dates to approximately 550,000 to 690,000 years ago, which is about four times older than the modern human mtDNA pool.” Recall our discussions of the genetic incursions of Neanderthals into human populations (and vice-versa). Briefly discuss human evolution in the following aspects (how are they adapted for life in certain environments or to use or process a particular nutrient or selection of certain human individuals):

Skin, hair, and eye color.-

Facial physiognomy.-

Metabolic adaptations (for example, lactose tolerance in groups derived from herders).

Hereditary metabolic errors of metabolism (diabetes type II, depression, circadian rhythm, etc.).

Answer 1

Human skin, hair, and eye color.

Skin is still one of the most definable variations in the human species. According to Darwin, it was the natural selection that is in place, as it is tied to geographical location as well as sun exposure.

Here is a picture of the ancestral root of human beings.

We can see here that the variation of light skin among Eurasian people evolved independently from different genetic backgrounds.

A prominent gene is in the play to determine the skin, hair and eye color called the "Major Facilitator Superfamily Domain Containing 12", (MFSD 12). This gene influences how melanin is produced and stored in the skin, thus affecting our skin color.

A research study suggests that Native Americans are genetically related to East Asians. Their initial settlement of the Americas occurring some 15–20,000 years ago, as they migrated from Eastern Siberia into North America. This is also resulting in sharing genetic variations in Native Americans with East Asians. This lighter skin color develops independently in Europe and East Asia.

A study also suggests that MFSD12 was under natural selection in East Asians. These people have split from Europeans around 40,000 years ago and were then carried over to America by ancient migrations of Native Americans.

Just like the skin color eye color is also studied more among the Europeans, especially the distinction between blue vs. brown eyes.