Final answer:
The existence of a unique gene in humans does not suggest that there is no common ancestor shared amongst all organisms, but instead it demonstrates that humans have undergone unique evolutionary changes. Genetic studies and DNA sequence homologies across species, including the close genetic relationship between humans and chimpanzees, support the theory of a common ancestry.
Step-by-step explanation:
If a gene found in the human genome is not homologous to any other known organisms, it does not necessarily mean that humans do not share a common ancestor with all other organisms. In fact, the presence of unique genes in the human genome may simply indicate that humans have undergone unique evolutionary changes that differentiate them from other species. However, this is not evidence against common ancestry because the vast majority of genetic code is homologous across different species, indicative of a shared common ancestor.
The concept of a common ancestor is further supported by numerous genetic studies that demonstrate homologies in the DNA sequences across varying species. For example, humans and chimpanzees share about 98% of their genes, suggesting a recent common ancestor. Moreover, mtDNA research shows that all humans can trace their lineage back to common ancestors who lived in Africa 200,000 years ago, further emphasizing the concept of common ancestry.
Therefore, while the unique gene in humans could imply that our species has experienced some distinct evolutionary events, it does not contradict the widely accepted scientific understanding that all life on Earth has evolved from a common ancestor. It rather highlights the complexity of the evolutionary process and the ongoing adaptations that differentiate species.