Which of the following statements is the most likely to be true of our species (Homo sapiens)?

Question

BlackTom AI · Accepted Answer

Modern human genomes, especially those of non-African populations, contain detectable Neanderthal DNA, so the first option is correct.

1) Relevant knowledge points and concepts
- Ancient DNA sequencing has recovered Neanderthal and Denisovan genomes, enabling direct comparison with modern human genomes.
- Genetic admixture (interbreeding) leaves identifiable segments of DNA in descendant populations.
- Studies estimate Neanderthal contribution to non-African humans at roughly 1–4% of the genome; Denisovan contribution is highest in some Oceanian populations.
- Humans and chimpanzees are separate species that share a common ancestor several million years ago.

2) Step-by-step reasoning
- Scientists sequenced Neanderthal genomes and aligned them with modern human genomes to look for shared derived alleles that are unlikely to result from chance or ancestral variation.
- Patterns of shared variants, length of introgressed haplotypes, and statistical models of population history indicate admixture events after Homo sapiens left Africa.
- These analyses consistently show that people with ancestry outside sub-Saharan Africa carry Neanderthal-derived DNA segments.

3) Calculations / intermediate steps (example magnitude)
- Human genome ≈ 3 billion base pairs. If Neanderthal ancestry is 1–4%:
  - 1% of 3,000,000,000 = 30,000,000 base pairs
  - 4% of 3,000,000,000 = 120,000,000 base pairs
  Thus non-African individuals typically retain tens of millions of base pairs of Neanderthal-derived sequence overall (scattered in many segments).

4) Why the correct answer is correct
- Direct sequencing evidence and population-genetic analyses demonstrate Neanderthal introgression into modern human genomes, producing the stated small amount of Neanderthal DNA in many present-day humans.

5) Why the other options are incorrect
- "Homo sapiens are the only hominid to have migrated out of Africa": False—Homo erectus and other hominins left Africa long before Homo sapiens.
- "There is no evidence that our ancestors ever interbred with Denisovans": False—genomic evidence shows Denisovan admixture, notably in Melanesian and some Asian populations.
- "there is no common ancestor for humans and chimpanzees": False—humans and chimpanzees share a recent common ancestor (divergence ~5–7 million years ago).

6) Conclusion
This evidence confirms the provided answer: It is likely that our genome contains a small amount of Neanderthal DNA.

Which of the following statements is the most likely to be true of our species (Homo sapiens)?单项选择题

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