The Part of DNA that Makes Us Different from Each Other

Recent research indicates that only 1.5 to 7 percent of the modern human genome is uniquely human. This means that the genes we possess which do not exist in our closest relatives like Neanderthals and Denisovans are a fraction of our overall genetic makeup. However, it's important to clarify some common misconceptions.

Clearing Up Misconceptions

Some individuals erroneously claim that our DNA is 99 percent identical to that of chimpanzees and that at least 2 percent of our genes have Neanderthal origins. This would add up to a total of 101 percent, which is logically inconsistent. These figures describe different aspects of genetics.

DNA vs. Genes

The chimpanzee number comes from a comparison of DNA, not genes. The Neanderthal numbers are based on ancestry, not genetic material or genes. Scientists have been examining stretches of DNA that appear to have changed since humans, Neanderthals, Denisovans, and other species diverged. This accounts for the 1.5 to 7 percent of genes mentioned.

The Mutated Genes

Most of the mutated genes unique to our species are regulatory genes. Many of these human-specific genes influence brain function and development, while others affect mRNA splicing, processing, and export. These regulatory genes are crucial in shaping our unique characteristics.

Timeline of Mutations

The chart illustrates the possible times at which our genes mutated, with many occurring between 200,000 and 2,000,000 years ago. This timing is listed as 'ka' years ago. The chart categorizes the mutations as either regulatory or other nonsynonymous. The upper part of the chart displays the most recent common ancestor (TMRSCA), while the lower part lists mutations that remain undated.

Regulatory Genes and Brain Function

One particularly interesting gene highlighted in the chart is NOVA1, which is a neuronal splicing factor that regulates the splicing of genes involved in synapse formation within the brain. This gene plays a significant role in brain development and function.

While space does not permit a detailed discussion of all genes, the chart includes several genes with interesting functions that contribute to our unique characteristics.

Genetic Diversity and Adaptation

It's also worth noting that while 1.5 to 7 percent of our genes are uniquely human, these genes work in concert with a vast array of other genetic elements to create the complex traits and behaviors that define our species.

As geneticists continue to unravel the mysteries of the human genome, our understanding of what makes us unique will undoubtedly expand. The interplay between these genes and their regulatory functions is crucial to our ongoing evolution and adaptation.

Comment: There are too many genes to discuss them individually. 1.5 to 7 percent of our genes works out to 600 to 2800 individual genes. This calculation assumes that we have roughly 40,000 genes, a bit more than 20,000 protein-coding genes, and a bit less than 20,000 non-coding genes.

The textbook I learned quantitative genetics from said that 'Genes hunt in packs.' This statement remains true more than a half-century after it was written. Genes do not operate in isolation; they work together in complex networks, contributing to the intricate and unique characteristics that define human biology.

Therefore, the specificity and interplay of these genes are what make humans different from each other and from our closest evolutionary relatives.

Final Thoughts

The genetic differences that make humans unique are not just a matter of a few isolated genes. They are the result of a complex interplay of regulatory and non-regulatory genes, working together to create the diverse and distinctive characteristics that define our species. Understanding these genetic differences is a continuous and evolving field of study.

Keywords: human DNA, genetic differences, unique human genes