圖1. 最近的研究已經揭露，尼安德塔人的遺傳結構，與一些現代人類是早起者傾向之間的一種關聯性。該項研究追溯到現代人類，與在歐亞大陸之尼安德塔人的混血。暗示，來自尼安德塔人的遺傳變異體曾經影響，其現代人類後代的晝夜節律。
Recent research has uncovered a link between Neanderthal genetics and the tendency for some modern humans to be early risers. This study traces back to the interbreeding of modern humans with Neanderthals in Eurasia, suggesting that genetic variants from Neanderthals have influenced the circadian rhythms of their modern human descendants.
A new paper in the journal Genome Biology and Evolution, published by Oxford University Press, finds that genetic material from Neanderthal ancestors may have contributed to the propensity of some people today to be “early risers,” the sort of people who are more comfortable getting up and going to bed earlier.
一篇由英國牛津大學出版社，發表於《基因體生物學暨演化》期刊的新論文發現，來自尼安德塔人祖先的遺傳物質，可能曾導致現代一些人是“早起者”的習性。這類人，早起及早睡，是較舒服的。
All anatomically modern humans trace their origin to Africa around 300 thousand years ago, where environmental factors shaped many of their biological features. Approximately seventy thousand years ago, the ancestors of modern Eurasian humans began to migrate out to Eurasia, where they encountered diverse new environments, including higher latitudes with greater seasonal variation in daylight and temperature.
所有解剖學上的現代人類，其起源皆回溯到，大約30萬年前的非洲。在那裡的環境因素，塑造了諸多他們生物學上的特性。大約七萬年前，現代歐亞人類的祖先，開始遷徙到歐亞大陸。在那裡，他們面臨了不同的新環境，包括具有在日光及溫度方面，較大季節性變化的更高緯度。
But other hominins, such as the Neanderthals and Denisovans, had lived in Eurasia for more than 400,000 years. These archaic hominins diverged from modern humans around 700,000 ago, and as a result, our ancestors and archaic hominins evolved under different environmental conditions.
不過其他古人類，諸如尼安德塔人及丹尼索瓦人，曾在歐亞大陸生存達40 多萬年。此些原始古人類，大約70萬年前與現代人類分道揚鑣。因此，結果我們的祖先及原始古人類，在不同環境條件下演化。
This resulted in the accumulation of lineage-specific genetic variation and phenotypes. When humans came to Eurasia, they interbred with the archaic hominins on the continent, and this created the potential for humans to gain genetic variants already adapted to these new environments.
這導致了，譜系特異性之遺傳變異及表型的累積。當人類來到歐亞大陸時，他們與該大陸上的原始古人類混血。因此，這為人類，獲得已經適應此些新環境的遺傳變異體，創造了可能性。
Previous work has demonstrated that much of the archaic hominin ancestry in modern humans was not beneficial and removed by natural selection, but some of the archaic hominin variants remaining in human populations show evidence of adaptation.
先前的研究已經佐證，大部分原始古人類血統，於現代人類中是無益的。因此，被自然選擇所剔除。不過，於人類種群中，殘留之諸多原始古人類的變異體，顯示了適應的證據。
For example, archaic genetic variants have been associated with differences in hemoglobin levels at higher altitudes in Tibetans, immune resistance to new pathogens, levels of skin pigmentation, and fat composition.
譬如，古老的遺傳變異體與，在較高海拔地區，藏族人的血紅素水平、對新病原體的免疫抵抗力、皮膚色素沉著水平及脂肪成分中的差異，一直被聯繫在一起。
Changes in the pattern and level of light exposure have biological and behavioral consequences that can lead to evolutionary adaptations. Scientists have previously explored the evolution of circadian adaptation in insects, plants, and fishes extensively, but it is not well studied in humans.
在曝光模式及程度的變化具有，會導致演化適應之生物學上及行為上的後果。先前，科學家們已經廣泛探索，於昆蟲、植物及魚類中，晝夜節律適應的演化。不過，沒充分研究過人類。
The Eurasian environments where Neanderthals and Denisovans lived for several hundred thousand years are located at higher latitudes with more variable daylight times than the landscape where modern humans evolved before leaving Africa. Thus, the researchers explored whether there was genetic evidence for differences in the circadian clocks of Neanderthals and modern humans.
在尼安德塔人及丹尼索瓦人生存，達數十萬年的歐亞環境，是座落於比現代人類在離開非洲之前，演化時的地帶，具有更富於變化之日光時間的較高緯度。因而，此些研究人員探索了，在尼安德塔人及現代人類之生理時鐘裡的差異，是否有遺傳證據。
The researchers defined a set of 246 circadian genes through a combination of literature search and expert knowledge. They found hundreds of genetic variants specific to each lineage with the potential to influence genes involved in the circadian clock.
藉由結合文獻檢索及專家知識，此些研究人員確定了，一組246個晝夜節律的基因。他們發現了，對每一譜系具有可能影響，涉及生理時鐘之基因，特有的數百種遺傳變異體。
Using artificial intelligence methods, they highlighted 28 circadian genes containing variants with potential to alter splicing in archaic humans and 16 circadian genes likely divergently regulated between present-day humans and archaic hominins.
使用人工智慧的方法，他們集中注意力於28個具有可能，有在原始人類中，改變基因移接之變異體的晝夜節律基因，及16個可能在今日人類與原始古人類間，不同調節的晝夜節律基因。
This indicated that there were likely functional differences between in the circadian clocks in archaic hominins and modern humans. Since the ancestors of Eurasian modern humans and Neanderthals interbred, it was thus possible that some humans could have obtained circadian variants from Neanderthals.
這顯示，於原始古人類及現代人類之生理時鐘間，很可能有功能上的差異。由於，歐亞現代人類的祖先與尼安德塔混血過。因此，某些人類可能曾經從尼安德塔人，獲得晝夜節律變異體，這是可能的。
To test this, the researchers explored whether introgressed genetic variants—variants that moved from Neanderthals into modern humans—have associations with the preferences of the body for wakefulness and sleep in large cohort of several hundred thousand people from the UK Biobank.
為了檢驗這一點，此些研究人員探索了，是否基因滲入的遺傳變異體(從尼安德塔人轉移到現代人類中的變異體)是否具有，與在來自英國生物銀行之數十萬大群人中，身體對清醒與睡眠之偏好的關聯性。
They found many introgressed variants with effects on sleep preference, and most strikingly, they found that these variants consistently increase morningness, the propensity to wake up early. This suggests a directional effect on the trait and is consistent with adaptations to high latitude observed in other animals.
他們發現了，許多對睡眠偏好具有影響之基因滲入的變異體。最引人注目的是，他們發現，這些變異體協調地增強，早起習性的晨間作息。
Increased morningness in humans is associated with a shortened period of the circadian clock. This is likely beneficial at higher latitudes, because it has been shown to enable faster alignment of sleep/wake with external timing cues.
於人類中，增強的晨間作息與縮短的生理時鐘週期有所關聯。在高緯度地區，這很可能是有益的。因為，這已經被證實，能使睡眠/甦醒隨著外部的計時刺激，更快調整。
Shortened circadian periods are required for synchronization to the extended summer light periods of high latitudes in fruit flies, and selection for shorter circadian periods has resulted in latitudinal clines of decreasing period with increasing latitude in natural fruit fly populations.
於果蠅中，為了與高緯度地區延長的夏季光照週期同步，需要縮短晝夜節律週期。因此，選擇較短的晝夜節律週期已經導致，於天然果蠅種群中，周期隨緯度增加，而減少的緯度梯度。
Therefore, the bias toward morningness in introgressed variants may indicate selection toward shortened circadian period in the populations living at high latitudes. The propensity to be a morning person could have been evolutionarily beneficial for our ancestors living in higher latitudes in Europe and thus would have been a Neanderthal genetic characteristic worth preserving.
因此，在基因滲入的變異體上，朝晨間作息的傾向可能顯示，生存於高緯度地區的人群，選擇朝縮短的晝夜節律週期。成為晨型(早起)人的習性，對咱們生存於歐洲較高緯度地區的祖先而言，演化上可能曾是有益的。因此或許曾是一種，值得保留之尼安德塔人的遺傳特性。
“By combining ancient DNA, large-scale genetic studies in modern humans, and artificial intelligence, we discovered substantial genetic differences in the circadian systems of Neanderthals and modern humans,” said the paper’s lead author, John A. Capra.
該項論文首要撰文人，John A. Capra宣稱：「於現代人類的諸多大規模遺傳學研究中，藉由結合遠古的DNA及人工智慧。我們發現了，在尼安德塔人與現代人類之晝夜節律系統中，可觀的遺傳差異。」
Then by analyzing the bits of Neanderthal DNA that remain in modern human genomes we discovered a striking trend: many of them have effects on the control of circadian genes in modern humans and these effects are predominantly in a consistent direction of increasing propensity to be a morning person.
然後藉由分析，持續存在於現代人類基因體中之尼安德特人的DNA片段，我們發現了一種驚人的趨勢：於現代人類中，其中許多對晝夜節律基因的控制具有諸多影響，且這些影響主要是朝，向增強成為早起人的一致方向。
This change is consistent with the effects of living at higher latitudes on the circadian clocks of animals and likely enables more rapid alignment of the circadian clock with changing seasonal light patterns.
此改變與生存在高緯度地區，對動物生理時鐘的影響是一致的，且很可能使生理時鐘，能隨著改變的季節性光照模式，更快速調整。
Our next steps include applying these analyses to more diverse modern human populations, exploring the effects of the Neanderthal variants we identified on the circadian clock in model systems, and applying similar analyses to other potentially adaptive traits.
我們的下一步包括，將這些分析應用於更多樣的現代人類種群、探索我們確認的尼安德塔人變異體，對模型系統中之生理時鐘的影響，及將類似的分析應用到，其他潛在的適應性特徵上。
網址：https://scitechdaily.com/ancient-neanderthal-dna-shaping-modern-morning-habits/
翻譯：許東榮
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