Why Don’t Scientists Use Specific Genes to Classify Fossils as Human or Non-Human?

This is a common question that delves into the intricacies of genetics and evolution. While there are indeed genes unique to the human genome, the use of these genes in classifying fossils as 'human' or 'non-human' is not as straightforward as it might seem. This article explores why current scientific methods do not employ this approach.

Understanding Human Genes

It is estimated that the human genome contains a vast number of genes. One recent count suggests there are 19,116 protein-coding genes, while another estimate includes 21,306 protein-coding and 21,856 non-coding genes.

However, not all of this genetic material is beneficial to us. A significant portion consists of parasitic DNA, transposable elements, and even viral DNA. These elements can complicate the process of identifying unique human genes.

Genetic Similarity Between Humans and Other Primates

The genetic similarity between humans and other primates, particularly chimpanzees and bonobos, is a topic of considerable interest. Internet sources often claim that humans and chimpanzees share 98-99% of their DNA, with protein-coding sequences being a staggering 99% identical. However, when considering the entire genome, the similarity is closer to 96%.

Moreover, the importance of this 96% overlap is often more relevant than the 99% similarity in protein-coding sequences. Many of the differences between humans and chimpanzees lie in gene regulation rather than protein sequences.

Regarding specific genes, about 7.1% of the proteins coded by human DNA differ from those in chimpanzees in at least one amino acid. While some of these differences might be insignificant, it is difficult to determine their significance accurately.

Scientific Challenges and Limitations

Even with sophisticated genome sequencing technology, some genes remain elusive due to near-duplicate sequences. Approximately 5% of the human genome is composed of repeated sequences, many of which are human-specific.

Despite these advancements, the exact percentage of similarity between humans and their closest relatives, such as chimpanzees and bonobos, is still under study. Comparisons can yield inconsistent results, making it challenging to apply a universal standard.

Genetic Differences and Classification

A closer look at the genetic differences between humans and chimpanzees reveals that there are roughly equal numbers of genes that are found in humans but not in chimpanzees, and vice versa. This observation contradicts the idea that humans are somehow more evolved or advanced than other primates.

There are a few genes that are unique to humans, a concept known as de novo genes, which were observed to have immune functions. However, many of these genes arose through gene amplification, where extra copies of existing genes were created.

A recent chart illustrating these genes shows that most fall into categories related to the immune system. The chart specifically highlights 845 genes that scientists suspect are involved in human-chimpanzee differences. These genes can be divided into categories, with a significant portion belonging to the dark blue category, indicating they are unique to human evolution.

Conclusion: The Complexity of Genetic Classification

Given the vast amount of genetic information and the complexity of human gene function, it is currently impractical to use specific genes to definitively classify fossils as 'human' or 'non-human.' The field of genetics is still in the process of understanding the exact roles of specific genes and how variations in these genes might affect human evolution.

As research continues, we may gain a better understanding of these genetic differences and their implications for classifying fossils. Nonetheless, the current state of science does not support the use of specific genes to definitively classify fossils.