古時保護人類的基因可能與現代疾病有關

胡靜

Scientists have compiled the largest database of ancient DNA based on the bones and teeth of almost 5，000 humans who lived across Western Europe and parts of Central Asia from 34，000 years ago until medieval times.

Analysis of this uniquely detailed pool of ancient genetic information suggests genes that may have once protected prehistoric hunter-gatherers or Bronze Age herders from harmful pathogens（病菌） may today increase the risk of neurodegenerative diseases such as multiple sclerosis and Alzheimer’s in Europeans.

By comparing the ancient DNA with modern-day samples， the researchers gained a new biological understanding of debilitating（衰弱的） disorders and physical traits in the present day.

One of the key findings from the first batch of research was connected to MS. It’s a complex condition shaped by multiple environmental and genetic factors with many potential symptoms. Northern Europeans are among those most prone to the the disease， the study noted， but the reasons why are little understood. By using the database， researchers found that genetic risk of having the condition correlates to the proportion of ancestry（血統） from a group of ancient pastoralists.

These nomadic（游牧的） herders， known as the Yamnaya， originated from the Pontic steppe. It’s thought they were the first horse riders， making them highly mobile. They brought specific genetic variants when they moved westward into Europe， these genetic variants may be beneficial to European populations in making the shift from hunting and gathering to farming.

The team concluded that the increased proportion of pastoralist ancestry in present-day northern Europeans might be partly responsible for the higher prevalence（流行） of the disease there.

Today， the protective benefits of these genetic variants are no longer as useful. We now lead very different lives to those of our ancestors in terms of hygiene， diet， and medical treatment options and we may be more susceptible to certain diseases than our ancestors were.

However， both then and now， all these genetic effects are modulated by the environment. For most traits， MS included， the genetic effects are the result of multiple genetic variants. Ultimately， we can’t say that MS came from Bronze Age populations， but these populations’ movements and environments contribute to differences in MS risk today.

（材料出自CNN網站，有刪改）

1. What can we know about the research？

A. Comparison was made between current DNA and ancient ones.

B. It indicates ancient genes still has protective benefits.

C. It indicates ancient genes are the major causes of MS.

D. The causes of MS were widely known before the study.

2. What does “prone” underlined in Paragraph 4 refer to？

A. Hard to imagine.

B. Extremely uncommon.

C. Resistant to a disease.

D. Easily infected.

3. What was the result of the specific genetic variants in Paragraph 5？

A. It contributed to the change in people’s agricultural development.

B. It made Yamnaya highly mobile.

C. It made Yamnaya weigh heavily on their life.

D. It led to Yamnaya’s movement to the western Europe.

4. Which statement will the author probably agree with？

A. Genetic variants is usually considered useful.

B. Genetic effects correlates with surroundings.

C. The environment have little impact on genetic effects.

D. Genetic variants was of little use in Bronze Age.

1. A。解析：細節理解題。材料第三段大意為“通過將古代DNA與現代樣本進行比較，研究人員對當今的衰弱性疾病和身體特征有了新的生物學理解”，選項A的意思為“比較了現有的和古代的DNA”，故選A。

2. D。解析：詞義猜測題。材料第四段最后兩句的大意為——研究指出北歐人是最容易患上這種疾病的人群之一，但人們對相關原因卻知之甚少；通過使用該數據庫，研究人員發現，患有這種疾病的遺傳風險與一群古代牧民的血統占比相關。據此，“prone”應該指的是容易患病，故選D。

3. A。解析：細節理解題。根據材料第五段最后一句中的“these genetic variants may be beneficial to European populations in making the shift from hunting and gathering to farming”，我們可知這些基因變異可能有利于歐洲人從狩獵和采集到耕作的轉變，故選A。

4. B。解析：推理判斷題。材料最后一段中的第二句提到“對于包括多發性硬化癥在內的大多數性狀來說，遺傳效應是多種遺傳變異的結果”，由此可推出“遺傳效應與周圍環境相關”，故選B。