Final answer:
Human genetic diversity is relatively low due to a bottleneck effect from our ancestors who migrated out of Africa around 200,000 years ago, not because humans are a species less than 10,000 years old. This diversity is shaped by natural selection and other pressures in human history, such as the advent of agriculture.
Step-by-step explanation:
The human species does have relatively low levels of genetic diversity compared to many other species, but this is not simply because humans are a recent species. Genetic information provided by mitochondrial DNA (mtDNA) indicates that all humans share common ancestors who lived in Africa about 200,000 years ago. This is much earlier than the 10,000-year timestamp associated with the advent of human civilization. One widely accepted explanation for the low genetic diversity in humans is the "Out of Africa" model, suggesting modern humans emerged first in Africa, and a population then expanded out of Africa, replaced other human species, and introduced a strong genetic bottleneck.
While the research by scientists like Dr. David Reed on coevolution with lice contributes to understanding the timeline of our species' evolution and diversity, these findings underscore that Homo sapiens is much older than 10,000 years. Additionally, the advent of agriculture and settled societies about 12,000 years ago introduced new selection pressures, resulting in genetic changes like lactase persistence in response to the use of bovine milk.
The extent of genetic diversity in humans is also influenced by the fact that all existing humans descended from a relatively small population exposed to various selection pressures over millennia, including challenges and adaptations related to environment, diet, and disease. This contributed to genetic adaptation and, over time, resulted in the genetic diversity we observe today, which is greatest in Africa due to its longer-established genetic lineage.