로그인 / 등록

雅思阅读-069-ghost-lineage-dna-in-everyone改编自-scientific-american-带音频

ielts 👁 9 · 💬 0 · 📅 2026-09-14
📌 雅思
← Blog 📡 RSS
A

雅思阅读 069 — Everyone Alive May Carry DNA from a 'Ghost Lineage' of Human Ancestors

改编自 Scientific American（2026-07，Jacek Krywko）。研究发表于 Science。

🎧 课文朗读音频（约 2 分钟）

Reading Passage

In a new Science study, scientists read the family tree buried inside modern genomes and turned up "ghost ancestors" in every population on Earth that no fossil records can account for.

Anatomically modern humans are just one branch of a broader family tree. The other branches — the archaic hominins, as scientists call them — include the Neanderthals, who lived across Europe and western Asia, and the Denisovans, who are known mostly from a handful of fossils found in Siberia and Tibet. These archaic lineages interbred with ancient human groups who had migrated out of Africa, which scientists can confirm by comparing rare preserved samples of their DNA with ours.

But did our direct ancestors interbreed with other long-lost hominin lineages before the first major migrations out of Africa roughly 70,000 years ago? Because we have never found any archaic hominin genomes in sub-Saharan Africa, scientists could not tell. To get around that limitation, a team co-led by Yulin Zhang, a computational biologist at the University of California, Berkeley, developed a new method for discovering archaic ancestry using only the DNA of humans from our time.

Our genomes contain not just one but thousands of family trees, each embedded in a short stretch of genetic code that has been shuffled around with each generation. Reconstructed correctly, these trees make it possible to estimate when each contribution to our DNA arrived. Most of the modern human genome coalesces to a common ancestor 100,000 to 200,000 years back, but DNA inherited from deeply divergent populations like Neanderthals or Denisovans does not — it produces a branch in the family tree that is unusually long.

The researchers analysed 503 contemporary genomes from across the world with a new mathematical model called TRACE (Tracking Archaic Contributions via ARG Estimation). It found that two per cent of the DNA in non-African genomes came from archaic lineages, consistent with prior research. Roughly half of that, or one per cent of the genome, matched sequenced Neanderthals, and a sliver matched Denisovans.

The rest, though — ranging from about 0.5 to one per cent depending on the population — matched nothing anyone has ever sequenced. This "ghost" lineage showed in every population Zhang and her colleagues examined and likely split off from our branch more than 500,000 years ago, around the time that Neanderthals and Denisovans did.

On top of that, the unknown lineage showed up in stretches of DNA that are almost devoid of Neanderthal and Denisovan genes — and which scientists had interpreted as uniquely our own. One of these regions sits around FOXP2, a gene linked to speech.

The results will need confirmation with another line of evidence. Further evidence could come from other computational methods or directly from as-yet-undiscovered fossils with preserved ancient DNA in sub-Saharan Africa. "Unless we get extraordinarily lucky with DNA preservation, we will likely have to rely on methods like TRACE," says Patrick F. Reilly, a computational biologist at Yale University.

"Perhaps these methods really have opened up a new frontier for looking at human evolution," says Priya Moorjani, a population geneticist at Berkeley and co-author of the study.

Questions

Questions 1–5: TRUE / FALSE / NOT GIVEN

  1. Neanderthal DNA has been found in fossils from Siberia and Tibet.
  2. No archaic hominin genomes have been found in sub-Saharan Africa.
  3. The TRACE method requires ancient DNA samples.
  4. The ghost lineage split from the modern human branch more than 500,000 years ago.
  5. The ghost lineage was found only in non-African populations.

Questions 6–10: Choose the correct letter, A, B, C or D.

  1. What does TRACE stand for?

    • A. Tracking Archaic Contributions via ARG Estimation
    • B. Testing Ancient Connections via DNA Extraction
    • C. Tracing Ancestral Chromosome Evolution
    • D. Tracking Archaic Cousins through Evidence

  2. What percentage of non-African DNA comes from Neanderthals?

    • A. 0.5%
    • B. 1%
    • C. 2%
    • D. 5%

  3. The ghost lineage DNA was found in regions previously thought to be

    • A. damaged by mutations
    • B. uniquely modern human
    • C. from Denisovans
    • D. from Neanderthals

  4. FOXP2 is a gene linked to

    • A. eye colour
    • B. speech
    • C. height
    • D. immunity

  5. According to Reilly, future confirmation of the ghost lineage may come from

    • A. new fossils with preserved DNA in Africa
    • B. cloning Neanderthals
    • C. studying chimpanzee DNA
    • D. examining human embryos

Questions 11–13: Complete the sentences. Choose NO MORE THAN TWO WORDS.

  1. The researchers analysed 503 __________ genomes from around the world.
  2. The "ghost" lineage split off from our branch around the time __________ and Denisovans did.
  3. The study was published in the journal __________.

Answers

  1. TRUE
  2. TRUE
  3. FALSE (只需要现代人 DNA)
  4. TRUE
  5. FALSE (在每一个被研究的人群中都发现了)
  6. A
  7. B
  8. B
  9. B
  10. A
  11. contemporary
  12. Neanderthals
  13. Science

Glossary

  • hominin /ˈhɒmɪnɪn/ n. 人科动物
  • archaic /ɑːˈkeɪɪk/ adj. 古老的
  • genome /ˈdʒiːnəʊm/ n. 基因组
  • lineage /ˈlɪniɪdʒ/ n. 血统，世系
  • recombination /ˌriːkɒmbɪˈneɪʃn/ n. 重组
  • coalesce /ˌkəʊəˈles/ v. 合并，融合
  • divergent /daɪˈvɜːdʒənt/ adj. 分歧的
  • computational /ˌkɒmpjuˈteɪʃənl/ adj. 计算的

💬 Comments (0)

No comments yet.