Homo antecessor

Credit: Mauricio Antón.

*Homo antecessor* is an extinct species of hominin that lived in Spain, England, the Mediterranean, inland Iberia and France during the Early Pleistocene.

## History

Sierra de Atapuerca is a northern Spain archeological site, from which *H. antecessor* are known. Gran Dolina ("great sinkhole") was first explored by Francisco Jordá Cerdá during a short field trip in 1966, where animal remains and stone tools were recovered. Though he lacked the resources to continue, Trinidad Torres in 1976 investigated the site to find *Ursus* fossils, and was instructed to visit Gran Dolina by the Edelweiss Speleological Team. Here, he found more remains of that genus and plesiomorphic human remains. This prompted massive exploration led by Emiliano Aguirre and later by José María Bermúdez de Castro, Eudald Carbonell and Juan Luis Arsuaga, with excavation restarting in 1992. Two years later, more human remains were discovered. In 1997, *H. antecessor* was named, with ATD-5, right mandibular fragment with molars and isolate teeth, assigned holotype. The epithet means "explorer", "pioneer" or "early settler", since Castro et al. believed they were the first human to leave Africa. 25 meters of Gran Dolina sediment is divided into 11 units: including TD1 and 11 ("trinchera dolina" and "sinkhole trench") and TD6 ("Aurora", the most researched unit and named after Aurora Martín Nájera, who discovered the first human remains from here).

Nearly 100 *H. antecessor* specimens are known, making at least 6 individuals. ATD6-15 and ATD6-69 are the most well preserved, possibly being of the same individual and with the most clear elucidate face anatomy. Field sessions from 2003-07 excavated a 140 square foot area and found 70 more specimens, including parts of the face, clavicle, forearm, digits, knees, vertebrae and ribs. Sima el Enfante ("elephant pit") in TE9 ("trinchera elefante") yields human remains, stone flakes and evidence of butchery. Gran Dolina has a stone too, assemblage similar to contemporaneous west European sites, which has led to speculation that they were made by the same species. However, this is still indeterminate since these sites yield no skeletal remains. 50 footprints from Happisburgh 1.2 million and 800,000 years old and discovered in 2014 may be referable since it is the only western European species known from this time. Among one individual, was a makeshift stone knife.

## Classification

*H. antecessor* has been proposed to have been a chronospecies between *H. erectus* and *H. heidelbergensis*. While *H. heidelbergensis* is an often-accepted predecessor to *H. neanderthalensis* and maybe *H. sapiens*, the derivation from *H. heidelbergensis* to *H. antecessor* is debatable. The discoverers note *H. antecessor* may have derived from African *H. erectus* migrating to the Iberian peninsula 1.2 million years ago, which directly-developed to *H. heidelbergensis* 0.8 million years ago, and then *H. neanderthalensis* 0.3 million years ago. *H. antecessor* has a face similar to *Homo sapiens*, so Castro et al. first posited it was the common ancestor of apomorphic humans. This would be scrutinized later. Jean-Jacques Hublin (2001) thought the Gran Dolina and contemporaneous Tighennif remains as a single populations (due to 14/15 dental traits), resurrecting *Homo mauritanicus* to group these. In 2007, Castro et al. found the Tighennif remains to be much larger and dentally similar to other African specimens , but recommending the usage of *H. ergaster mauritanicus* to house the North African Early Pleistocene specimens. Esteban Sarmiento et al. (2007) questioned the validity of *H. antecessor* since *Homo heidelbergensis* is known roughly from the same time and place and because the type is a child, it is questionable, since the autapomorphic features could have simply being normal for the ontogenetic series (such as face restructuring caused by climatic adaptation). In 2009, Richard Klein stated skepticism for *H. antecessor* being ancestral to *Homo heidelbergensis*, interpreting the former as an offshoot that split before the human/Neanderthal split. Frido Welker et al. (2020) found the same by analyzing dental proteins from ATD6-92.

"Homo erectus antecessor" was a name made-up by Wikipedia users. It has not been used formally in literature or even proposed anywhere else. Studies suggest it and *Homo erectus* split sometime during the Early Pleistocene based on morphological differences, dental morphology, geographic and temporal segregation. "H. atapuerquensis" and "H. burgalensis" were names once considered, but they were discarded in favour of *H. antecessor* to avoid excessive local-ness. The naming of *Homo bodoensis* finds:

A hominid evolution display at the Houston Museum of Natural Science bears a diagram of *Homo antecessor* and uses the Buia UA 31 skull as a representative of the species and using a geologic time range of 1.1 million-900,000 thousand years. A later study confirmed that it is a *Homo erectus*.

## Description

*H. antecessor* face anatomy is most referenced from ATD6-69, a 10-11.5 year-old child, and fragmentary specimens. It is very similar to *Homo sapiens* and East Asian Middle Pleistocene plesiomorphic humans in this sense. The face is fully flat and the zygomaticoalveolar crest is curved. Sarah Freidline et al. (2013) used statistics to determine that the facial features would not have been lost when maturity was reached, and that the modem face evolved and disappeared many times, which was later found not unlikely since facial anatomy is influenced by diet and environment. The nasals are much like *Homo sapiens*. The mandible is gracile and unlike plesiomorphic hominins, but bears plesiomorphic features such as a apomorphic-shaped mandibular notch and a apomorphic, vertical alveolar part. The pterygoid tubercle is large and like Neanderthals, but unlike them, there is no retromolar space. The shovel-shaped incisors are a character of Eurasian hominins, including apomorphic. The cingulum on the canines and the essential ridge are like derived species, retaining cuspules near the tip of the bordering incisor, like plesiomorphic species. The upper premolars have crowns that are derived and nearly symmetrical, with a lingual cusp and a cingulum with longitudinal grooves towards the cheek. The upper molars are like Neanderthals. The mandibular teeth are plesiomorphic; the P3 has a highly asymmetrical crown and complex tooth root system, the P3 is smaller than the P4 like derived hominins and the M1 is smaller than the M2 and the cusps of the molar crowns make a Y like in early *Homo*. Enamel distribution is Neanderthal-like, with thicker layers in the periphery than the cusps. The enamel thickness and the proportion of the tooth covering the gums is variable, possibly due to sexual dimorphism (females with smaller teeth, somewhat thicker enamel and less gum coverage. However, *H. antecessor* is known to have thinner enamel in some specimens, as in Neanderthals and rare in *Homo*. The parietals are flattened, conjoining the midline to make a tent-like profile found in African and Asian *Homo erectus*. Like African *Homo erectus*, the temporal styloid process is below the ear and fused to the skull base. The brow is prominent and the upper margin of the squamous is part of the temporals, and convex like derived hominins.

ATD6-50 has a notably large clavicle that indicates an absolute size of 162.3–186.8 centimeters (5-6 feet 2-4 inches), mean of 174.5 centimeters (5 feet 9 inches. Adult, possibly male due to size or female due to gracility, radius ATD6-43, may have been 172.5 centimeters tall based on radial length and comparisons with apomorphic populations. Based on the metatarsal, males would have stood 173 centimeters high and females 168.9. The ankle could handle high stress, which indicates a heavy, robust body like the Neanderthal. Based on footprint length/body size rations, the Happisburgh prints are preserved well enough to be consistent with individuals 93-173 centimeters tall, meaning some of the trackmakers were children. The three largest footprints (individuals 160 centimeters, 163 centimeters and 173 centimeters tall, 48-53 kilograms heavy) were in the size range for *H. antecessor*, *Homo heidelbergensis* and Neanderthals. Two atlases are known, which is rare for ancient hominins; they are indistinguishable from *Homo sapiens*. The axis has an angle of the spinous process jutting to about 19°, comparable with Neanderthals and humans. The vertebral foramen is narrower than apomorphic humans, but otherwise aligns quite well. The only complete clavicle is ATD6-50, which is thicker than a apomorphic human, which indicates that they were platycleidic. This would make the chest broad, with proximal curvature on par with Neanderthals and much more pronounced distal curvature. The sternum was narrow, the acromion is smaller than apomorphic forms and the shoulder blade is standard for all *Homo* who were not skilled climbers but rather good at launching projectiles.

ATD6-43 is an incomplete radius estimated to be 257 millimeters long. It is oddly straight for a northern specimen, similar to apomorphic humans. This could be explained as an ancestral long-limbed form or a high brachial index. The cross section is rather round and gracile compared to recent species. The radial neck, like plesiomorphic species, is long, giving leverage to the biceps brachii. The radial tuberosity is anteriorly placed. Like plesiomorphic species, the femur bears a developed trochanteric fossa and posterior crest, which are variable among apomorphic human populations. ATD6-22 and -56 are kneecaps that are subrectangular, rather than the more common subtriangular shape, and rather narrow like apomorphic humans. They are small and thin, falling to the lower variation in apomorphic humans. The apex is not well developed, leaving small attachment sites to the patellar tendon. The medial and lateral facets are about the same size in -56 and the medial is larger in -22; the lateral is more common in apomorphic humans. The lateral facet lays on a flat area rather than only on the vastus notch. This is infrequent in *Homo*. The phalanges and metatarsals of the foot are similar to later humans, but the big toe bone is robust, which may be related to how they pushed off the ground. The talus is very long and high, where the facet connects to the trochlea, which may be related to body weight transmission. The long gtrochlea causes a short neck on the talus, which bridges the head of the talus connecting the toes, and the talus body to the leg. This somewhat converges with Neanderthals, where this is explained through a heavier and more robust body to alleviate stress. This would have permitted greater flexion.

## Paleobiology

Castro et al. (2020) estimated ATD6-112 died between 5.3-6.6 years of age, based on tooth formation in chimpanzees and apomorphic humans. The molars are hardly worn, which means tooth eruption had just happened, which correlates with life history. If this is true, then *H. antecessor* had a longer childhood that may have allowed for more cognitive development.

### Paleopathology

ATD6-69 has an ectopic M3 that erupted improperly and impacted the M2, where eruption was then blocked. Though this is common in apomorphic humans (as high as 50% in certain populations), M2 impaction is rare (0.08-2.3%), and can lead to secondary lesions such as dental cavities, root resorption, dentigerous or keratocysts. ATD6-1 bears severe dental attrition and abrasion of tooth crowns and bone resorption in the root so that the root canals are exposed in the canines. This is consistent with gum disease caused by teeth overload, specifically by using the mouth to carry objects. This is also found in Sima de los Huesos Neanderthals from Atapuerca. ATD6-56, a left knee, has a 4.7x15 millimeter osteophyte on the interior margin, which are typically caused in response to osteoarthritis (which in turn is caused by old age or improper joint loading through misaligned bones or ligament laxity. Improper loading was likely the factor, and frequent squatting and kneeling may enable this injury. However, if ATD6-22 is from the same individual, which bears no injury, it is unlikely to be the cause. If so, then it would be caused by local trauma, such as surrounding soft tissue strain due to intense activity or a left femoral or tibial fracture. This is indeterminate, since neither bones are associated. ATD6-124 has a 25.8-8 millimeter lesion on the medial of the 4th metatarsal. consistent with a march fracture, which most often occur by soldiers, long-distance runners and flatfooted people who engage in repeated, intense activity. Neanderthals would combat this by evolving more robust skeletons, though from Sima de los Huesos this is also seen.

### Technology

*H. antecessor* produced a simple industry also known from Early Pleistocene Spain sites such as Barranc de a Boella and Galeria, where they prepared and sharpened the cores before flaking, with crude bifaces and a degree of standardized tool types, possibly ancestral to Acheulean tools. TD6 tools were probably used in butchering since they bear abrasions fitting with flesh-tool contact. 84 tools, mostly small unmodified quartzite pebbles with percussive damage that may have been pounded against bone, tools were recovered from TD6.3. 41% of the assemblage are crude, large (38x30x11 millimeter) flakes that may have been produced through knapping or difficulty working with materials. They used unipolar longitudinal methods to compensate for a lack of pre-planning. Most tools from the older half of TD6.2 (total 831), with knappers that made many materials including chert (indicating expansion to find better materials), fewer pebble production, spent more time knapping flakes and being less economic with materials (most cores discarded could have been made to make more flakes). Irregular blanks were modified into workable pieces before flaking. This allowed them to use centripetal and bipolar methods. 62 flakes below 20 millimeters in height are found. 3 flakes of much higher quality, thinner and longer may have been made by the same person. Retouched notches, spines, denticulates, points, scrapers and a single chopper are known, which are rare in Early Pleistocene Europe. TD6.1 has 124 poorly preserved (since hyenas used the area as a latrine) tools, the layer not having pebbles and cores, with 44 of them indeterminate. The flakes are much smaller than others, being 28x27x11 millimeters, with 10 below 20 millimeters and 3 exceeding 60 millimeters. They seem to have been produced using the same methods as in TD6.2. They retouched larger flakes here, with 14 larger flakes averaging 35x26x14 millimeters. a marginally retouched flake, a notch, 3 spines, 7 denticulate sidescrapers and a denticulate point are found.

### Diet

Large animal carcasses found at the Grand Dolina locality appear to have been transported their intact. This likely means that *Homo antecessor* deployed hunting parties, who delayed consuming their kills until return to camp. This shows great signs of social cooperation, labour division and food sharing. About 16 animal species have been reported: bush-antlered deer, red deer, bison, wild boars, *Stephanorhinus etruscus*, Stenon zebras, mammoths, Mosbach wolves, *Vulpes praeglacialis*, Gran Dolina bears, spotted hyenas and a lynx. The deer are the most common found in Gran Dolina. The humid and montane environment allowed growth of olive, beech, mastic, hazelnuts and chestnut trees, which were probable food sources that are more common in TD7 and 8 as the interglacial progresses and the environment becomes westter. In TD6, pollen derives from junipers and oaks. Trees likely grew along water, with hills and ridges dominated by grasses. TD6 bears individuals that may have consumed hackberries, which are traditionally used as medicine more than proper food, since they provide little flesh. They likely would not have been able to cook and wield fire, with molars indicating frequent consumption of gritter and mechanically challenging foods than later European *Homo*, such as raw meat and underground storage organs.

 File:Homo antecessor overlooking settlement.png
8 young adult and child individuals from Gran Dolina were found to bear cut marks and fracturing indicating cannibalism, being the 2nd most common remains with signs of butchering. They utilized these bodies, and may be the reason why the preserved elements are so badly damaged. No complete skulls are present and the face and the back of the skull that are preserved are percussed, with the muscle attachments in the face and skull base cut off. They likely modified the face in this way to access the brain. The crown of the head was likely smashed, resulting on impact scars at the teeth and gum line. Several skull fragments bear signs of peeling. The ribs bear cuts along muscle attachment points consistent with defleshing. ATD6-39 bears cuts along the rib's length, possibly related with disembowelment. The nape muscles were sliced off, and the head and neck likely detached from the body. The vertebrae were often cut, peeled and percussed. All clavicle muscles were sawed off, disconnecting the shoulder. ATD6-43, a radius, was cut up and peeled. The femur was shattered, likely to extract marrow. Hands and feet are percussed, cut and peeled, variably, probably a result from dismembering. The meatier areas were prepared and the remaining were discarded, probably for dietary reasons and maybe under dire circumstanves. The face bears more cuts than animal faces, which is typically interpreted as exocannibalism in fossil humans. However, Yolanda Fernandez-Jalvo et al. (1999) reviewed evidence and found that the butcher that dismembered their faces was less familiar with human anatomy than that of animals, or that the face required more cuts. Nonetheless, *H. antecessor* is abundant in cannibalized individuals. Carbonell (2010) hypothesized that they hunted individuals from foreign tribes exocannibalize. Jesús Rodríguez et al. (2019) argue that this is more consistent with cannibalizing foreigners who had died of natural causes, as to maximize food, especially since apomorphic hunter-gatherer groups have high juvenile mortality rates. The remains show no sign of ritualistic handling or intentional burial, so some believe that the individuals (of which the majority are children or adolescents) were killed due to ecological issues stemming from an abundance of hominins in a single catchment area. That is, hominins were more common in the area than local fauna, so exocannibalism was preferred by members of this species.

## Paleoecology

Several charcoal particles from TD6 are known, probably from a fire well outside of the cave. No burnt bones or evidence of cooking are found in occupation sites, and fire would not emerge elsewhere in the world until ~400,000 years later. Rather than using fire, they likely physiologically withstood the cold by using a high-protein diet. The climate was similar to today's despite climate cycles, with the coldest average of 2 °C (36 °F) in December and January and the hottest of 18 °C (64 °F) in August. Freezing may have reached from November to March, but olive and oak presence suggests subfreezing was infrequent. TD6 seems to have been several degrees warmer than the present, and they likely migrated from the Mediterranean shore into inland Iberia when colder glacials transitioned to warmer glacials, when grasslands dominated and vacating any other time. They may have followed water as they migrated, most likely the Ebro River, which is closest to Atapuerca. TE9 indicates a generally warm climate. The Happisburgh prints were deposited in estuarine mudflats with pine, spruce, alder (in wetter areas) and birch-dominated forests with heath patches and grasslands, which are consistent with the cooler beginning or ending of an interglacial.

## Synonyms

* "H. erectus antecessor" (context)
* "H. atapuerquensis"
* "H. burgalensis"
* "H. edulis"[*citation needed*]
* "H. europaeus"[*citation needed*]
* "Pseudhomo antecessor"
* *H. atapuerca* (=ATE9-1)
* *H. sapiens antecessor*

## Notable Specimens

* ATD6-15 and ATD-69 "Gran Dolina Boy" (el chico de la Gran Dolina): The most well-preserved individuals are ATD6-15 AND ATD6-69; a frontal and maxilla, which have since been named "Gran Dolina Boy" (el chico de la Gran Dolina), of a 10-year-old boy who is 859,000-782,000 years old.
* ATD6-92: Direct ESR dating of ATD6-92 in 2018 estimates an age of 624-949 ka, with further magnetostratigraphic information from TD6 estimates 772-949 ka.
* Sima del Elephante molar: In 2007, a molar 1.2-1.1 million years old was discovered in the nearby Sima del Elefante locality. This belongs to a 20-25 year-old individual.
* ATD6-5: The holotype of *H. antecessor*, a right mandibular fragment with molars. Isolate teeth were recovered nearby.
* ATD6-50: A very large adult clavicle that is assumed to have been a male (based on size) who was 162.3-186.8 centimeters tall.
* ATD6-43: An incomplete adult radius of either a man (based on size) or a woman (based on gracility), who was 172.5 centimeters tall based on apomorphic populations. The radius is 257 millimeters long, and similar to the proportions of apomorphic humans. It presents evidence of cannibalism through cutting and peeling.
* ATD6-56 and ATD6-22: Kneecaps, the only ones known. -56 bears an abnormal bone growth, but -22 bears no pathologies.
* ATD6-112: A 5.3-6.6 year-old individual represented a permanent upper and lower first molar.
* ATD6-124: A right fourth metatarsal with a march fracture.
* ATD6-39: A specimen with cuts across the ribs representing cannibalistic disembowelment.
* ATE9-1: The fossil was discovered by Rosa Huguet and the Atapuerca Team on June 30, 2007 after finding one tooth in the Sima del Elefante (the Elephant Pit), and is now housed at the Museo de la Evolución Humana in Spain. In 2008, Eudald Carbonell et al. published their findings in Nature, who dated the fossil using biostratigraphy, litostratigraphy and technique cosmogenic nuclides. The fossil was referred to *Homo antecessor* upon discovery, but was reduced to *H. sp*. due to the morphology and other indeterminate aspects of the remains. ATE9-1 represents one of the first Europeans, colonizing the region 1.2 million years ago. This hominin was very primitive, and leads researchers to believe hominins reached west Europe ~1.5 million years ago. Alongside the ATE9-1 mandible were *Homo antecessor*, stone tools and bones showing evidence of butchery. ATE9-1 is slender, which suggests the individual who produced this fossil was female, in her 20s. However, older and same-age stone tools have been found in France, Italy and Spain (~1.5 million years old). This discovery and species may influence hominin evolution theories, such as Out-Of-Africa. 32 Oldowan-like flint tools were found with ATE9-1. The specimen preserves socket of left premolar 4 to the socket of right molar 1. Some teeth are fully complete, while others are incomplete or fragmented. Some characteristics are most similar to the Dmanisi and oldest African *Homo*, but also has several differentiating features. For example, the jaw has several apomorphic characteristics and an incipient chin.

## References

1. ↑ https://onlinelibrary.wiley.com/doi/book/10.1002/9781444342499
2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 https://en.wikipedia.org/wiki/Homo\_antecessor
3. ↑ https://books.google.co.il/books?id=5TRHOmTUTP4C
4. ↑ https://books.google.es/books?id=iNdKDgAAQBAJ
5. ↑ https://en.wikipedia.org/wiki/Talk:Homo\_erectus#H.\_erectus\_subspp
6. ↑ https://nutcrackerman.com/2014/07/01/20-anos-de-homo-antecessor/
7. ↑ https://onlinelibrary.wiley.com/doi/10.1002/evan.21929
8. ↑ https://twitter.com/AlexTheTurtle5/status/1549813862991527936
9. ↑ https://www.sciencedirect.com/science/article/abs/pii/S0047248422001671
10. ↑ https://phys.org/news/2023-01-neanderthals-species-dentition-characterized-thin.html
11. ↑ https://www.sciencedirect.com/science/article/abs/pii/S0047248421001391
12. ↑ https://link.springer.com/article/10.1007/s10816-016-9306-y#citeas
13. ↑ https://www.elperiodico.com/es/sociedad/20080327/atapuerca-aumenta-antigueedad-primer-europeo-67265
14. ↑ https://www.nature.com/articles/nature06815
15. ↑ https://web.archive.org/web/20160311212546/http://www.atapuerca.tv/atapuerca/yacimiento\_elefante
16. ↑ https://www.nature.com/articles/news.2008.691
17. ↑ https://www.sciencedirect.com/science/article/abs/pii/S0047248411000820