我們的基因演化是為了抵禦古老的威脅，但在現代社會，其中一些變化可能對我們不利

 Recently The New York Times reported the following:

Where Do Autoimmune Diseases Come From? (2/2)

Our genes evolved to fight ancient threats, but in the modern world, some of those changes may be turning against us.

By David Quammen (David Quammen is a science journalist and author of 19 books. This piece is part of “Disease States,” his new series on evolution and disease.)

Published Oct. 20, 2026, Updated Oct. 22, 2026

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Today, according to the researchers, those same gene variants seem to be having an opposite effect. With infectious diseases better controlled and the prevalence of M.S. on the rise, “we again observe a striking correlation with changes in our environment, including lifestyle choices and improved hygiene, which no longer favours the previous genetic architecture,” they wrote. In other words, genes that once protected us may now put us at risk.

Another study from an international team of researchers looked at a more recent historical moment of abrupt demographic change: the Black Death. This 14th-century pandemic of plague (caused by the bacterium Yersinia pestis, which is carried by fleas, which are carried by rats) swept through Europe, the Middle East and northern Africa between 1346 and 1353, killing as much as 30 to 50 percent of the population in those areas.

The researchers scrutinized DNA sequences from the dead in England and Denmark, some buried just before the plague years, some during and some after. One of their sources was East Smithfield, a Black Death mass burial site just east of the Tower of London. There and elsewhere, the researchers found four immunity-related gene variants in the genomes of more people buried after the plague than before or during it, suggesting that those variants had conferred a survival advantage. After a dispute of their mathematical methods by another team, the researchers refocused their assertion on one variant. That variant, evidently adaptive against plague, is now a known risk factor for Crohn’s disease. So it seems that the Black Death, like the transition to pastoralism during the Bronze Age, may have been a selective event that increased the jeopardy of future generations to autoimmune diseases.

Although the Oxford team, in its study of M.S., called this situation a case of outdated “genetic architecture,” there’s another metaphor that makes the same point more vividly. Recall the adage about the failings of military leadership: that generals spend their peacetime preparing to fight the last war, rather than the next one. They cling to obsolete tactics and strategies and weaponry — things that worked well in the past — despite the march of time and the arrival of novelties. This is apparently what evolution has done with the gene variants that many of us carry today. Autoimmune diseases in the 21st century may represent the human immune system’s efforts to fight a war that was once cataclysmic and is now less so against ubiquitous and incurable infectious diseases.

For some people, the miseries of M.S. or lupus or other autoimmune maladies is a cruel misfortune. Others are luckier. For instance, me: I have only my psoriasis (inherited from my father, who inherited it from a lineage of Norwegian country people) as a reminder that my own immune system is ready and eager, too eager, to fight the last war — the war between a Bronze Age herdsman and a virus he picked up from one of his goats.

Translation

自體免疫疾病從何而來？ （2/2）

我們的基因演化是為了抵禦古老的威脅，但在現代社會，其中一些變化可能對我們不利

（繼續）

如今，研究人員表示，同樣的基因變異似乎產生了相反的影響。隨著傳染病得到更好的控制，多發性硬化症（MS）的盛行率不斷上升，他們寫道:「我們再次觀察到，這些疾病與環境變化之間存在顯著的相關性，包括生活方式的選擇和衛生條件的改善，而這些變化不再有利於先前的基因結構」。換句話說，曾經保護我們的基因現在可能使我們面臨風險。

另一項由國際研究團隊進行的研究則著重於近期歷史上人口急劇變化的時期：黑死病。 14世紀的鼠疫大流行（由鼠疫耶爾森菌引起，菌由跳蚤攜帶，跳蚤又被老鼠攜帶）在1346年至1353年間席捲歐洲、中東和北非，導致這些地區30%至50%的人口死亡。

研究人員仔細分析了英格蘭和丹麥死者的DNA序列，其中一些死者埋葬於鼠疫爆發前，一些埋葬於鼠疫期間，還有一些埋葬於鼠疫之後。他們的樣本來源之一是East Smithfield，這是位於倫敦塔東側的黑死病萬人坑。研究人員在那裡以及其他地方發現，在鼠疫之後埋葬的人的基因組中，有四種與免疫相關的基因變異，而鼠疫之前或期間埋葬的人的基因組中則沒有這種變異，這表明這些變異賦予了他們生存優勢。在另一研究團隊對他們的數學方法提出質疑後，研究人員將研究重點重新放在其中一種變異上。這種變異顯然具有抵抗鼠疫的適應性，如今已被證實是克隆氏症的已知風險因素之一。因此，黑死病似乎就像青銅時代向畜牧業的過渡一樣，可能是一種選擇性事件，增加了後代罹患自體免疫疾病的風險。

儘管牛津大學的研究團隊在對多發性硬化症 (MS)的研究中將這種情況稱為過時的“基因結構”，但還有另一個比喻能更生動地表達同樣的觀點。想想那句關於軍事領導失敗的諺語：將軍們在和平時期為最後一場戰爭做準備，而不是之後的戰爭。他們固守過時的戰術、戰略和武器 - 那些過去行之有效的方法 - 儘管時代在變遷，新事物層出不窮。這顯然就是進化對我們許多人今天攜帶的基因變異所做的。 21世紀的自體免疫疾病可能代表人類免疫系統試圖對抗一場曾經災難性的戰爭，一場曾經是災難性的戰爭，如今對抗的是無所不在且無法治癒的傳染病，這場戰爭的災難性後果已經減輕。

對某些人來說，多發性硬化症、紅斑性狼瘡或其他自體免疫疾病所帶來的痛苦是一種殘酷的不幸。有些人則幸運得多。例如我：我只有銀屑病（遺傳自我父親，而他又是從挪威鄉村家族遺傳的），它提醒自己的免疫系統隨時準備著，甚至過於渴望地去打那場戰爭- 一場青銅時代牧羊人與他從山羊身上感染的病毒之間的戰爭。

              So, evolution doesn’t have purposes, only results. Darwinian natural selection doesn’t shape creatures to be “better” or “higher” in some objective, transcendent sense — it shapes creatures to succeed in the here and now. And what works in one environment or period of time may prove harmful in another. More specifically, scientists have found evidence of natural selection for certain gene variants during the Bronze Age. Those same variants may increase the risk of autoimmune disease in people who carry them today. Apparently, the Black Death, like the transition to pastoralism during the Bronze Age, may have been a selective event that increased the chance for future generations to have autoimmune diseases.

Note:

1. MS is Multiple Sclerosis (多發性硬化症). It is used in the context of evolutionary medicine to describe a chronic autoimmune disease where the body's immune system mistakenly attacks the central nervous system. The attacks explain how gene variants that once protected ancient humans from infectious diseases have now become risk factors for developing Multiple Sclerosis due to modern hygiene and lifestyle changes.