This Fossil Breaks the Human Family Tree

At Gran Dolina in northern Spain, a series of human fossils dating to roughly 850,000 years ago has created an increasingly difficult problem for the conventional story of our ancestry. The species is Homo Antecessor, an early human whose anatomy combines traits that once seemed separated by vast evolutionary distances. Its face has features unexpectedly similar to Homo Sapiens, while other parts of its anatomy retain much older characteristics. Protein evidence places its population extremely near the evolutionary division that eventually produced Homo Sapiens on one side and Neanderthals and Denisovans on the other. Now the parietal bones from Gran Dolina are adding another piece to that puzzle. Their total thickness falls within the range found among Homo Sapiens and Neanderthals rather than the generally thicker condition associated with Homo Erectus and several other earlier humans. Even the internal construction of these bones follows a pattern shared with later humans. This raises an intriguing question. If Homo Antecessor really represents the direct last common ancestor of Homo Sapiens and Neanderthals, why is an 850,000 year old population in Europe already displaying features that eventually characterize Homo Sapiens, hundreds of thousands of years before the earliest, widely accepted members of our species appear in Africa? The newest evidence comes from three adult parietal fragments from the TD6 deposits at Gran Dolina, identified as ATD6-115, ATD6-128, and ATD6-401. The first reaches roughly 41.5 x 34.6 mm, while the second reaches about 49.6 x 36.4 mm. Researchers examined the fragments through microcomputed tomography, allowing them to look inside the cranial wall instead of treating it as a single sheet of bone. A parietal bone contains an outer compact table, an internal spongy region called the diploe, and an inner compact table bordering the cranial cavity. This internal architecture provides information that simple measurements across the entire bone can conceal. In all three Homo antecessor specimens, the diploe forms the largest component, accounting for approximately 41-50% of total cranial thickness. That general arrangement is also characteristic of Homo Sapiens and Neanderthals. Total vault thickness itself falls inside their ranges, and below the generally greater thickness documented in Homo erectus and other humans from the early Pleistocene. This is not an exact anatomical match with Homo Sapiens, and that distinction is important. Homo antecessor has a relatively thinner outer table and a relatively thicker inner table than the comparative Homo Sapiens and Neanderthal samples. The evidence therefore points toward a mosaic rather than a skull that could simply be mistaken for ours. Cranial thickness also varies according to several biological influences, so it cannot independently establish an evolutionary relationship. Even so, the pattern matters because it joins other anatomical traits already placing Homo antecessor in an unusual position. Instead of looking uniformly primitive, an individual living approximately 850,000 years ago possesses a combination of ancient characteristics and features associated with populations that appear much later. The parietal evidence therefore strengthens an anatomical pattern already visible elsewhere in the Grandolina fossils rather than creating that pattern by itself. The face is the most famous example. Homo antecessor possesses a relatively flattened midface and delicate cheek region that researchers have compared with Homo Sapiens. These characteristics contrast strongly with the projecting and strongly built facial architecture characteristic of later Neanderthals. This has led to a striking reversal in how some supposedly modern anatomy can be interpreted. A flatter facial configuration need not have originated recently with Homo Sapiens. Instead, important parts of that configuration could be ancient traits inherited from a population existing before the Homo Sapiens and Neanderthal evolutionary branches diverged. Under that interpretation, Neanderthals evolved their distinctive facial anatomy after the split, while Homo Sapiens retained and subsequently modified aspects of a much older facial pattern. What appears modern in Homo antecessor could therefore represent ancestral anatomy rather than an unexpectedly advanced preview of Homo Sapiens. That possibility became more significant when molecular evidence entered the debate. Protein sequences recovered from Homo antecessor dental enamel placed the Grandolina population near the lineage ancestral to Homo Sapiens, Neanderthals, and Denisovans. The protein evidence did not establish Homo antecessor as the direct last common ancestor. Instead, it supported a position extremely near the common ancestral population, compatible with Homo antecessor, representing a sister lineage near the point from which those later groups emerged. This distinction prevents the fossil evidence from becoming more definitive than it actually is. The original interpretation of Homo antecessor nevertheless went further. When the species was named in 1997, its combination of primitive and derived anatomy led its describers to propose it as a candidate for the last common ancestor of Neanderthals and modern humans. Later research has refined that proposal without making the underlying evolutionary question disappear. Chronology has actually made the question more interesting. Genetic work has generally placed the division between the Homo Sapiens lineage and the lineage containing Neanderthals and Denisovans well before 500,000 years ago. Some analyses, particularly those examining the rate of dental evolution required by different evolutionary trees, push the common ancestral population toward approximately 800,000 years ago or earlier. That creates a problem for Homo heidelbergensis as a simple universal ancestor, particularly when European middle Pleistocene fossils increasingly display Neanderthal affinities. Homo antecessor, at roughly 800,000 to 900,000 years old, occupies a far more intriguing chronological position. It is old enough to sit near the required evolutionary branching point while already possessing facial and cranial characteristics linking it in unexpected ways with much later populations. Yet another piece of evidence initially seems to pull in the opposite direction, the brain. Living Homo Sapiens have a characteristically globular cranial form. The brain case is relatively rounded rather than elongated with bulging parietal regions, a taller frontal region and changes involving the cerebellar region. This globular condition is often treated as one of the clearest anatomical signatures of Homo Sapiens. The evolutionary history revealed by fossil brain cases, however, shows that globularity arrived surprisingly late. Early Homo Sapiens, around 300,000 years ago, already possessed brain volumes within the range of living humans, but their brain shape remained different. The earliest examples retain a more elongated configuration, intermediate in important respects between earlier humans and the later globular Homo Sapiens condition. Jebel Irhoud makes this particularly clear. The Moroccan fossils dating to roughly 300,000 years ago combine surprisingly modern facial anatomy with an elongated brain case. Their brains were already large, yet enlargement had happened along an older evolutionary pathway rather than through the distinctive globular geometry characteristic of living Homo Sapiens. This demonstrates that facial modernization, brain enlargement and brain globularization were not a single evolutionary transformation. They happened at different times. The face could acquire a Sapiens-like configuration while the brain case retained an older form, and brain volume could enter the living human range before the brain acquired living human geometry. The significance for Homo Antecessor is substantial because it provides a mechanism for understanding how an ancient population could possess Sapiens-like facial or parietal characteristics without possessing a fully Sapiens-like brain. The evolutionary transformation toward globularity continued much later. Homo Sapiens fossils dating between approximately 130,000 and 100,000 years ago have more globular brain cases than the earliest members of the lineage, but they still differ from the range characteristic of living people. Fossils younger than roughly 35,000 years ago overlap living human variation much more fully. The transformation therefore appears gradual, taking place between approximately 100,000 and 35,000 years ago rather than occurring suddenly at the origin of Homo Sapiens. Two changes are especially important, increasing parietal bulging and enlargement or reorganization around the cerebellar region. This happened during the evolution of Homo Sapiens itself, long after the evolutionary division from Neanderthals. That creates an important distinction when interpreting the Grandolina parietals. Parietal bone thickness is not the same characteristic as parietal bulging. The new Homo Antecessor evidence concerns the thickness and internal architecture of the cranial wall. Brain globularization concerns the geometry of the endocranial cavity and, indirectly, the organization and developmental growth of the brain inside it. Finding Homo Sapiens-like parietal thickness in Homo Antecessor therefore cannot demonstrate that Homo Antecessor possessed a modern globular brain. In fact, the later history of Homo Sapiens argues strongly against making that jump. Even humans living around 300,000 years ago lacked the full globular condition. What Homo Antecessor demonstrates is something subtler. Some components of cranial anatomy associated with later humans existed enormously earlier than the completed anatomical package that characterizes living Homo Sapiens. This is where the evolutionary geography becomes particularly interesting. If Homo Antecessor were demonstrated to be the direct last common ancestor of Homo Sapiens and Neanderthals, a population belonging to our direct ancestral species existed in Europe about 850,000 years ago. Under that scenario, the evolutionary story could not begin with an exclusively African Homo Sapiens lineage already detached from everything occurring in Eurasia at that time. The ancestral population preceding the Homo Sapiens-Neanderthal split would already have a Eurasian distribution, and traits inherited by Homo Sapiens could trace back to populations inhabiting that broader Old World landscape. The flattened facial architecture and aspects of parietal construction would then precede the later African appearance of Homo Sapiens by more than half a million years. But this would not by itself overturn the out-of-Africa theory. The distinction is crucial. Out of Africa, theorists primarily argue that Homo Sapiens evolved in Africa and that populations of Homo Sapiens later expanded from Africa into Eurasia. Finding the common ancestor in Spain concerns an earlier stage of evolution. An ancestral species could inhabit Europe and Africa, split into daughter populations, and still give rise to Homo Sapiens primarily within Africa. Grandolina proves that Homo Antecessor lived in western Eurasia. It cannot tell us that the species originated there. A fossil locality identifies where a population existed, not the geographical birthplace of its entire species. The direct ancestor hypothesis would therefore reshape the deeper background of out-of-Africa without automatically disproving the later African evolution and expansion of Homo Sapiens. It would nevertheless make the simplest version of the story much harder to sustain. Instead of a long geographically isolated African trajectory generating one modern characteristic after another, human evolution would look increasingly like a sequence of traits assembled at different times across populations occupying a much wider region. A Sapiens-like facial structure could already exist around 850,000 years ago in Spain. Parietal thickness and internal cranial architecture could also fall within the later Homo Sapiens and Neanderthal ranges at the same ancient locality. Hundreds of thousands of years afterward, early Homo Sapiens in Africa could retain a comparatively elongated brain case while possessing a large brain and a relatively modern face. Only still later would evolutionary changes in Homo Sapiens generate the strongly globular brain configuration characteristic of people today. The geographic implications become even broader if the common ancestral population itself was widely distributed. Early humans repeatedly moved between Africa and Well at the moment I'm certainly looking again at the whole question of a recent African origin for modern humans because that's been the leading idea of the last 20 years, that we had a recent African origin, that we came out of Africa and we replaced all these other humans. By approximately 1.8 million years ago, human populations were already established at Dmanisi in Georgia, demonstrating that movement beyond Africa began extraordinarily early. By the age of Homo Antecessor, western Eurasia had already become part of that inhabited world. If populations exchanged genes across interconnected regions, asking whether every anatomical trait was simply African or Eurasian becomes less informative than determining where particular branches differentiated and where particular traits first appeared. A direct Homo Antecessor ancestry would make Europe part of the immediate geographical background to the later Homo Sapiens Neanderthal split, even if Homo Sapiens itself subsequently emerged within Africa. This also explains why Homo Antecessor remains such an important test case rather than a solved ancestor. The sample is small, the adult parietal material is fragmentary, and the protein evidence currently favors placement near the common ancestral branch rather than demonstrating direct ancestry. Researchers therefore have good reasons to describe Homo Antecessor as a population near the evolutionary root shared by Homo Sapiens, Neanderthals and Denisovans. Yet that cautious placement is itself remarkable. An 850,000 year old European human already combines an unexpectedly modern looking face with cranial bone characteristics that overlap much later humans, while molecular evidence independently places the population near one of the most important branching points in our evolutionary history. Perhaps the greatest lesson from Homo Antecessor is therefore that the anatomy defining Homo Sapiens did not appear as a single package in one evolutionary moment. Some facial characteristics appear to have deep ancestry. Cranial wall architecture has roots extending back toward the era of the common ancestral population. Large brain size arrived before fully modern brain shape, and the globular brain emerged through a later transformation inside the Homo Sapiens lineage itself. If Homo Antecessor eventually proves to sit directly on our ancestral line, the implications will reach far beyond the classification of fossils from one Spanish cave. The last common ancestor of Homo Sapiens and Neanderthals would be represented in western Eurasia, carrying parts of an anatomical pattern eventually inherited by us, long before anyone recognizable as Homo Sapiens existed. Thank you for watching. Homo Antecessor still occupies an uncertain position on the human family tree, but each new fragment from Grandolina narrows the possibilities. The question now is not simply whether an ancient European population looked unexpectedly similar to us. It is whether those similarities survived because Homo Antecessor stood beside our common ancestor, or because we are looking directly at that ancestor itself. The difference between those possibilities is remarkably small anatomically, yet enormous for understanding where the deepest foundations of Homo Sapiens actually began.