‘Distinct’ Facial Features Have Been Around For A Very Long Time
A new study suggests that human facial features are found deep within our ancestry. Some say that the similarities between the facial features of modern humans and the controversial Early Pleistocene hominin species called Homo antecessor suggests that they were the last common ancestors of both modern humans, Denisovans, and Neanderthals. Others say that’s not the right place for them on the evolutionary tree. But how can researchers find out the right location for H. antecessor when the fossil records are fragmentary and ancient DNA Early and Middle Pleistocene hominins has yet to be recovered? It’s time to bring in the mighty tooth once again!
Co-researcher of the current study, Frido Welker, explained the importance of analyzing dental enamel to Ancient Origins, “ Dental enamel is the densest/hardest tissue in the human skeleton. We notice that when we compare protein preservation in dental enamel to protein preservation in dentine or bone, which are less dense skeletal tissues, the proteins in dental enamel are always better/more preserved/abundant. As a result, dental enamel is the most optimal tissue when searching for ancient hominin genetic information (let’s say, between 500,000 and 2,000,000 years old).”
A tooth of Homo antecessor was studied using ancient protein analysis. Credit: Prof. José María Bermúdez de Castro
So with their dental enamel specimens in hand – from the molars of H. antecessor from Atapuerca, Spain (dated to 949,000–772,000 years ago) and Homo erectus from Dmanisi, Georgia (approximately 1.77 million years old) - the researchers conducted a phylogenetic analysis (analyzing ancient protein sequences to find the evolutionary relationship of species) and set off to find the right place for H. antecessor on the evolutionary tree.
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What Do We Know About Homo Antecessor ?
H. antecessor is a controversial species in the genus Homo because their remains have so far only been identified in the Gran Dolina TD6 assemblage in Atapuerca, Spain. They are believed to have lived from 1.2 million to 800,000 years ago, making them one of the earliest human-like species in Europe.
Gran Dolina preserves a long-term record of Pleistocene hominin populations. Credit: Prof. José María Bermúdez de Castro
Antecessor is a Latin word meaning “predecessor, vanguard, scout, or pioneer.” The first example of what would become known as H. antecessor was discovered in 1994 and the researchers of the current study state that since then “over 170 human fossil remains have been recovered from level TD6 of the Gran Dolina site of the Sierra de Atapuerca.” The unique combination of features seen in the crania, mandibles, and dental features led to a suggestion that the human fossils be referred to as their own species in 1997. Since then the relationship between H. antecessor with other hominins in Eurasia – Homo erectus , Neanderthals, Denisovans, and modern humans, has been debated.
The debate about the appearance of an adult H. antecessor has also been going on for years. In 2012, for example, The Smithsonian raised this criticism: “Since most of the features tying H. antecessor to modern people were found in juveniles—whose bodies and physical features change as they grow up and go through puberty—it’s possible that H. antecessor adults didn’t really look much like H. sapiens at all. And if that’s the case, then it’s hard to argue the species had an ancestor-descendent relationship with us.”
Skeletal remains of Homo antecessor . Credit: Prof. José María Bermúdez de Castro
Human Facial Features May Have Appeared Earlier
As you have probably noticed over the years, the story of Pleistocene hominins is still changing as more information comes to light. The evolutionary relationships of H. antecessor and other hominin groups is not always clear as dates are shifted around and new members are added or places are shifted on the evolutionary tree.
In the case of H. antecessor, some of their more modern facial features have had them placed before us and our neighbors, the Neanderthals and Denisovans. According to the research paper previous studies “have confirmed that H. antecessor exhibits the oldest known modern-like face in the fossil record.”
But the new study, published today in the journal Nature, states that H. antecessor was closely related to the last common ancestor of Homo sapiens , Neanderthals, and Denisovans. Specifically, the researchers, Frido Welker, Enrico Cappellini and their colleagues, believe that the right place for H. antecessor is as “a close sister lineage to subsequent Middle and Late Pleistocene hominins, including modern humans, Neanderthals and Denisovans.”
Skulls of Homo Erectus, Sapiens, Neanderthalensis and Antecessor. ( Creativemarc /Adobe Stock)
They write that this placement “implies that the modern-like face of H. antecessor—that is, similar to that of modern humans—may have a considerably deep ancestry in the genus Homo, and that the cranial morphology of Neanderthals represents a derived form.” Furthermore, the results of their analyses suggest “that these features appeared in Early Pleistocene hominins, and were retained by Neanderthals and lost by modern humans.
In 2014 French sculptor Élisabeth Daynès reconstructed the image of a young H. antecessor boy based on an incomplete skull from Atapuerca, Spain. Her work is in the Museo de la Evolución Humana in Burgos, Spain.
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Forensic reconstruction of a juvenile Homo antecessor by Élisabeth Daynès (2014), Museo de la Evolución Humana, Burgos, Spain. ( CC BY SA 4.0 ) Note his facial features.
When asked about the possibility of a new adult H. antecessor facial reconstruction on the horizon, Professor José María Bermúdez de Castro told Ancient Origins that the researchers “hope to find more remains of this species and to be able to reconstruct the face of an adult” in the future.
What Can This Teach Us About the Features of Neanderthals and Denisovans?
Professor José María Bermúdez de Castro also explained why the researchers have suggested that the Neanderthal cranium is a derived, rather than primitive, form telling Ancient Origins that the environment likely played a role, “It is possible that the very particular and exclusive face of Neanderthals is related, either with adaptation to climatic conditions, or with their type of diet. There is no clear answer on the matter, but many speculations.”
When asked why Homo antecessor features remained more present in Neanderthals than in modern humans, Professor Bermúdez de Castro hypothesized to Ancient Origins that:
“Although the face of Homo antecessor is very similar to that of Homo sapiens (modern-like) it is true that this species seems to have a number of characters scattered in different anatomical regions, which were inherited much later by Neanderthals. However, I wonder if that scattered set of characters is more important than the face. Always from the field of speculation, the fact that Homo antecessor is a European species may also be a reason to find more similarities with Neanderthals, a species originated and evolved in Eurasia.”
Since there is still an ongoing debate about what Denisovans may have looked like as well, Ancient Origins asked Professor Bermúdez de Castro to weigh-in on that hominin group’s appearance.
“In my view, the face of Denisovans would not be much different from that of older Neanderthals.” Professor Bermúdez de Castro said, “For example, we know very well the faces of the humans recovered at the Sima de los Huesos site in the Sierra de Atapuerca (Spain), who share their RNA with the Denisovans and who can be considered as "ancient Neanderthals". Therefore, the face of the Denisovans could be not very different from that of the humans recovered from the Sima de los Huesos.”
Those Teeth Were Made for Chomping!
Finally, we also asked the researchers if they learned anything new about the general function of the teeth, that is, eating, and what these prehistoric choppers can tell us about the diet of H. antecessor. Professor Bermúdez de Castro’s response may surprise you, unless you’ve already read a couple of previous studies regarding their diet on Ancient Origins. The professor said:
“All hominins are omnivores. We can eat any food. The diet depends on the food that we have available. In the Sierra de Atapuerca, 800,000 years ago, there was a milder climate than today and there was plenty of food available: fruits, berries, insects, eggs, fish, amphibians, reptiles, etc., as well as various species of mammals for hunting. All this could be part of the Homo antecessor menu, including other human beings. The oldest known cannibalism in the history of humanity has been verified in Homo antecessor. Undoubtedly, it was a territorial cannibalism, since the Sierra de Atapuerca region was very rich in natural resources, including many water springs.”
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Model of a male Homo antecessor of Atapuerca mountains possibly practicing cannibalism. (Ibeas Museum, Burgos, Spain) ( Jose Luis Martinez Alvarez/ CC BY SA 2.0 )
Despite the diverse natural resources available, H. antecessor were cannibals…and probably not because they needed the calories.
Let’s Keep Mapping the Evolutionary Tree…
Now that the researchers believe they have found the right place for H. antecessor on the evolutionary tree , what will they do next?
Welker says that this study has set the stage for future projects. When asked what his own next project will be, he told Ancient Origins, “More hominins! We are keen to explore the further use of ancient protein analysis when studying human evolution in a range of time periods, sites, and hominin taxa.”
We look forward to seeing where these studies will take us as we continue to discover more about our ancient ancestors and evolutionary neighbors.
Digital reconstruction of specimen ATD6-69 from the Homo antecessor collection. Computerized microtomography (micro-CT) techniques were used to perform this reconstruction. Credit: Prof. Laura Martín-Francés
Top Image: Homo antecessor shared many facial features with modern humans. Source: Terrae Antiqvae