Ancient Teeth Reveal Connections Between Denisovans and Homo Erectus

For the first time, researchers have successfully extracted significant amounts of preserved protein from fossils attributed to ancient humans, specifically Homo erectus.

While previous discoveries of H. erectus fossils exist, this is the first instance revealing substantial insights into this species. The recovered protein indicates interbreeding between H. erectus and another ancient Asian hominin, the Denisovans.

H. erectus is recognized as one of the longest-lived and widely dispersed species of hominins. They emerged in Africa approximately 2 million years ago and reached Eurasia around 1.8 million years ago, as evidenced by fossils found in Dmanisi, Georgia. Notably, some traveled to the island of Java, now part of Indonesia, where they thrived until roughly 108,000 years ago.

In 2020, a research team led by Fried Welker from the University of Copenhagen successfully extracted protein from the tooth enamel of a H. erectus specimen from Dmanisi. While this provided proof that proteins could be recovered from ancient fossils, John Hawkes of the University of Wisconsin-Madison noted that the data gathered was underwhelming, lacking substantial information about the Dmanisi fossils.

Recently, a team led by Qiao Meifu at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing analyzed proteins from six designated H. erectus teeth. These specimens are approximately 400,000 years old and were sourced from various Chinese sites, including Zhoukoudian, Hexian, and Sunjiadong. The team identified a distinctive protein called amelogenin Y, finding that five teeth belonged to males, while one belonged to a female.

Mr. Fu did not respond to interview requests.

Among the six teeth analyzed, two unique protein variants were identified. One variant had not been observed in any human population, suggesting it is characteristic of H. erectus. The other variant was previously identified in Denisovans, who inhabited East Asia during the last several hundred thousand years. This raises intriguing questions about Denisovan interbreeding with an unidentified hominin group, potentially linked to H. erectus.

Hawkes acknowledges that while this interpretation is plausible, it’s merely one of three possible explanations for the data.

The critical uncertainty for Hawkes lies in whether the six teeth genuinely belong to H. erectus. Although results from the three sites seem reliable, the isolated tooth raises doubts regarding its classification, as its morphology does not match known H. erectus characteristics. Additionally, the historical context of H. erectus fossils in China complicates this determination, since all previously discovered fossils date back over a million years.

Hawkes posits an alternative scenario where the group may not actually be H. erectus at all but could be Denisovan. This potential mutation in protein may reflect variation within Denisovan populations. Supporting this idea, recent research analyzing Denisovan DNA across 30 modern human populations has indicated connections from three distinct Denisovan groups, each of which interbred with early Homo sapiens.

Alternatively, if the interbreeding between Denisovans and H. erectus did occur, Hu’s team suggested it hints at a lineage of Denisovans possessing H. erectus traits.

To resolve these possibilities, more fossil and molecular data will be essential, as noted by Hawkes.

Such uncertainties are not uncommon, as the study of ancient proteins is still in its nascent stages. Hawkes compares these early challenges to those faced during the initial exploration of ancient DNA.

<section class="ArticleTopics" data-component-name="article-topics">
    <p class="ArticleTopics__Heading">Topics:</p>
    <ul class="ArticleTopics__List">
        <li class="ArticleTopics__ListItem">Evolution of Humanity<span>/</span></li>
        <li class="ArticleTopics__ListItem">Ancient Humans</li>
    </ul>
</section>