Recently CNN.com reported the following:
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| (Source: CNN) |
What proteins in prehistoric teeth reveal about Stone Age
sex between early human species (1/2)
CNN- By Katie Hunt
UPDATED MAY 14, 2026
A prehistoric human known as Homo erectus was the first of
our forerunners to leave Africa, crossing continents and ultimately roaming the
planet for almost 2 million years. But with scarce genetic material available
to study, the species remains a major mystery in human origins.
Now, scientists have retrieved ancient proteins from six teeth unearthed in China that, for the first time, reveal a molecular link between Homo erectus and later human species, including our own: Homo sapiens.
“This is a major step forward in tying together the broken branches of our human evolutionary tree,” said Ryan McRae, a paleoanthropologist at the Smithsonian National Museum of Natural History in Washington, DC, who was not involved in the study. “Homo erectus has long been a bit of an enigma.”
Homo erectus remains have been found in Africa, Asia and Europe; however, obtaining informative molecular data such as DNA has proved challenging given the fossils’ age and poor preservation.
In a study published Wednesday in the scientific journal Nature, Chinese geneticist Fu Qiaomei and her colleagues successfully extracted and analyzed ancient enamel proteins from the teeth unearthed at three sites in China. All the teeth date from around 400,000 years ago.
Proteins, which are made up of sequences of amino acids, are more robust than ancient DNA, a fragile molecule that degrades relatively easily. Proteins contain far less detailed information, but they can still shed some light on a specimen’s evolutionary history.
Fu, a professor at the Institute of Vertebrate Paleontology and Paleoanthropology, part of the Chinese Academy of Sciences in Beijing, and her team used what they described as a new, less invasive technique to study fossils without damaging their morphology.
Rather than drilling, they used acid etching to remove a small sample of enamel from the teeth. The team did not try to recover DNA from the fossils after failing to extract DNA from animal fossils of the same age from the same sites. Fu said it was hard to get DNA, but she would never give up.
Unknown variant discovered
The researchers found that the specimens from the three
sites in China shared two amino acid variants, one of which was previously
unknown. This finding, the researchers reasoned, suggested the teeth all
belonged to the same species.
The second variant had previously been identified in Denisovans, another shadowy species of ancient human, and also in some modern human populations.
That other human species shared this variant suggested that Denisovans had once interbred with Homo erectus, and then, at some later point, Denisovans mated with Homo sapiens, according to the study.
As a result, traces of Denisovan DNA live on in some humans today — something interbreeding geneticists call admixture.
Similarly, modern human populations have some Neanderthal ancestry — a legacy of past interactions with that species that went extinct about 40,000 years ago. Denisovans also interbred with Neanderthals.
Modern human populations in Southeast Asia have the highest Denisovan ancestry, suggesting the two groups once crossed paths there.
(to be continued)
Translation
史前牙齒中的蛋白質揭示出石器時代早期人類物種之間有那樣的性接觸（1/2）
一種名為直立人（Homo erectus）的史前人類，是我們祖先中第一個走出非洲。他們跨越各大洲，最終在地球上活動了將近二百萬年。然而，由於可供研究的遺傳物質極為稀少，這個物種仍是人類起源研究中的重大謎團。
如今，科學家從中國出土的六顆牙齒中提取出古老蛋白質，首次揭示了直立人與後來人類物種（包括我們智人 Homo sapiens）之間的分子聯繫。
位於美國華盛頓特區Smithsonian國家自然歷史博物館的古人類學家 Ryan McRae（沒有參與此研究）表示：「這是在串聯人類演化樹斷裂分支方面的一大進展」;「直立人長期以來一直有點神秘」。
直立人的遺骸已在非洲、亞洲與歐洲被發現；然而，由於化石年代久遠且保存狀況不佳，要取得具資訊價值的分子資料（例如 DNA）一直非常困難。
在週三發表於科學期刊《Nature》的一項研究中，中國遺傳學家Fu Qiaomei及其同事成功從中國三處遺址出土的牙齒中提取並分析古代琺瑯質蛋白。這些牙齒都可追溯至約四十萬年前。
蛋白質由胺基酸序列組成，相比古代 DNA 更為穩定；DNA 是一種脆弱的分子，容易隨時間降解。雖然蛋白質所含資訊遠少於 DNA，但仍能為標本的演化歷史提供一些線索。
Fu是中國科學院北京脊椎動物古生物與古人類研究所教授。她與團隊使用一種他們稱為「侵入性較低」的新技術，在不破壞化石的原有特性下進行研究。
研究人員與其鑽探，改為使用酸蝕法從牙齒琺瑯質中去除少量樣本。由於先前無法從同年代、同遺址的動物化石中提取 DNA，因此團隊並未嘗試從這些化石中回收 DNA。Fu表示，雖然取得 DNA 很困難，但她永遠不會放棄。
發現未知的變異體
研究人員發現，來自中國三處遺址的樣本共享兩種胺基酸變異體，其中一種變異體此前從未被發現。研究團隊因此推測，這些牙齒都屬於同一物種。
另一種變異體此前曾在丹尼索瓦人（Denisovans）- 另一種神秘古人類 - 以及部分現代人族群中被發現。
研究指出，其他人類物種也擁有這種變異體，顯示丹尼索瓦人曾與直立人發生過雜交，而之後丹尼索瓦人又與智人交配。
結果是，部分現代人至今仍保有丹尼索瓦人的 DNA 痕跡 - 遺傳學家將這種跨物種混合稱為「基因混合」（admixture）。
同樣地，現代人族群中也帶有部分尼安德塔人血統，這是與該物種過去互動的遺留痕跡；尼安德塔人大約在四萬年前滅絕。丹尼索瓦人也曾與尼安德塔人雜交。
現今東南亞的人類族群擁有最高比例的丹尼索瓦人血統，顯示這兩個族群過去可能曾在當地相遇。
（待續）
