Full Breakdown
Ancient Retrovirus Insertion May Influence Chimpanzee Brain Gene
By Drooid · · How we work
Core Findings
A new study in *Science Advances* reports that the endogenous retrovirus PTERV1, which entered the genome of chimpanzees (Pan troglodytes) about four million years ago, inserted DNA near the long-non-coding RNA gene LINC00662. The insertion silences this gene in chimpanzee cells, whereas the same gene remains active in humans. Experiments with human brain organoids showed that disabling LINC00662 reduces neuronal maturation and the growth of dendrites and axons. Conversely, removing the viral insertion from chimpanzee stem cells re-activates LINC00662, indicating the insertion’s direct regulatory effect.
Background & Context
Humans and chimpanzees share roughly 98.8 % of their DNA, yet human brains are about three times larger. Retroviral sequences are common remnants of ancient infections and can modulate nearby genes. PTERV1 is found in chimpanzees and other African apes but is absent from the human genome, making it a prime candidate for explaining species-specific brain development differences.
Data & Statistics
- DNA similarity between the species: 1.2 % difference.
- Relative brain size: human brain ? 3 × larger than chimpanzee brain.
- Timing of viral insertion: approximately 4 million years ago.
- Gene affected: LINC00662, active during early human brain development.
Official Statements & Responses
Lead author Patricia Gerdes, a molecular neurogeneticist at Lund University, emphasized that the study does not claim the viral insertion alone determines brain size or cognition. She noted that many genetic and developmental factors shape brain evolution, and that re-activating LINC00662 in adult chimpanzees would not reverse earlier developmental trajectories. Gerdes also cautioned that the full range of LINC00662’s functions in humans remains unknown, and that the potential consequences of a similar insertion occurring in humans are speculative.
Verbatim Quotes
- “We found it active during early human brain development, and our experiments suggest it helps [human] brain cells mature and grow extensions,” — Patricia Gerdes, lead author
- “We do not yet know all of LINC00662's roles in the human body, or what the loss of its activity means for chimpanzees as a whole,” — Patricia Gerdes, lead author
- “If humans had the same insertion, it probably would have switched off LINC00662 and altered the development of brain cells,” — Patricia Gerdes, lead author
- “In our experiment, removing the insertion from chimpanzee stem cells restored LINC00662 activity. That shows the insertion contributes to switching off this gene. It does not show that removing it would transform brain development,” — Patricia Gerdes, lead author