Ust'-Ishim man

• 1. Introduction

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  Ust'-Ishim man is the name given to a single fossil bone, a left femur, that emerged from a Siberian riverbank in 2008. Nikolai Peristov, a Russian sculptor who specializes in carving mammoth ivory, spotted it protruding from the bank of the Irtysh River. He brought it to a forensic investigator, who suggested the bone might be human. Researchers eventually confirmed it belonged to a male hunter-gatherer, and they named the fossil after the Ust-Ishimsky District of Siberia, where it turned up. How old was this man, and what could a single thigh bone possibly reveal about him? Was he connected to the Neanderthals who once shared his world, and does anyone alive today carry a trace of his lineage?

• 2. Sequencing An Ancient Genome

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  Paleoanthropologists at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, examined the femur closely. Carbon dating placed the bone at 45,000 years old, making it the oldest human fossil dated by that method. Despite that age, the DNA inside had survived intact, letting scientists sequence a complete genome to contemporary standards of quality. The result ranks among the oldest modern human genomes ever fully decoded. That genome held a record of his ancestry stretching back through his Y-chromosome and mitochondrial lines alike.

• 3. Y-DNA And Mitochondrial Lines

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  Ust'-Ishim man's Y-chromosome placed him in haplogroup K-M2308, though scientists first classified him more broadly as K(xLT). A 2016 study by Poznik and colleagues refined that placement. It showed he was K2(xK2b,K2c,K2d,K2e), positive for some but not all of the mutations that define K2a, including M2308. Before that research, scientists had assumed haplogroups K2a and NO were the same lineage. Some Y-DNA family trees have since been updated to reflect Poznik's finding that K-M2308 is a direct ancestor of haplogroup NO. Other studies argue his haplogroup more likely belongs to the NO clade itself, rather than the more diverged K2 clade.

  On his mother's side, Ust'-Ishim man belonged to mitochondrial haplogroup R*, differing from the root R sequence by a single mutation. Both his paternal and maternal haplogroups, along with their descendant subclades, are now found across Eurasia, Oceania, and the Americas. Yet no known population today descends directly from Ust'-Ishim man's own specific branches of either line.

• 4. Placing Him In The Family Tree

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  Autosomal DNA places him in a narrow window of history. That window opens after the first wave of modern humans left Africa, roughly 270,000 years ago. It closes before that population split into separate regional branches around 45,000 years ago. As a result, he was not closely tied to the next two major eastward migrations out of Africa. One route followed the coast of South Asia; the other cut north-east through Central Asia.

  Compared with other ancient remains, Ust'-Ishim man's closest genetic match is Tianyuan man, found near Beijing and dated to 42,000-39,000 years ago. He also shows close ties to Mal'ta boy, or MA-1, a child who lived about 24,000 years ago. That child's remains were found along the Bolshaya Belaya River, near modern Irkutsk in Siberia. A third close match is La Braña man, a hunter-gatherer who lived roughly 8,000 years ago in what is now Spain. None of these ancient men were Neanderthals, but Ust'-Ishim man's own genome carried traces of that other hominin species too.

• 5. Neanderthal Kinship

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  Modern humans and Neanderthals interbred sometime between 86,000-37,000 years ago, according to comparisons across modern genomes. That mixing left non-African populations today carrying between 1.5-2.1 percent Neanderthal DNA. In most modern people, that Neanderthal DNA survives only in short, broken fragments. In Ust'-Ishim man's genome, by contrast, the Neanderthal DNA appears in long, unbroken clusters. That pattern suggests he lived in the immediate aftermath of the interbreeding between the two species. Analysis of his genome let scientists narrow the likely date of that mating to between 52,000-58,000 years ago.

  Scientists have not checked whether Ust'-Ishim man shared any relationship with the Denisovans, another extinct human relative. Denisovans left descendants among people in Oceania and Asia today, a link that has never been tested for Ust'-Ishim man himself.

• 6. Affinity With Living Populations

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  Ust'-Ishim man was equally related to modern East Asians, modern Oceanians, and certain ancient West Eurasians, including the Goyet specimen. Modern Europeans, by contrast, trace closer ties to other ancient remains instead. Researchers said this pattern fits a hypothesis. Perhaps modern Europeans partly descend from a population that took no part in humanity's earliest spread into Europe and Asia.

  A 2016 study identified modern Tibetans as the population sharing the most alleles with Ust'-Ishim man. A 2017 study went further, reporting that "Siberian and East Asian populations shared 38% of their ancestry" with him. A 2021 study reached a different conclusion. It found that Ust'-Ishim man and another ancient individual, Oase 1, showed no greater affinity to any modern western or eastern Eurasian population. That result suggested neither individual contributed ancestry to later Eurasian populations, contradicting what earlier studies had shown.

• 7. An Ancient East Eurasian Wave

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  A 2022 study placed Ust'-Ishim man within an Initial Upper Paleolithic wave, more than 45,000 years old. Researchers named this group the Ancient East Eurasians, describing the wave as "a population movement with uniform genetic features and material culture." He shared deep ancestry with other members of this group, including the Bacho Kiro individuals, the Oase specimen, and Tianyuan man. That ancestry also extended to the forebears of modern Papuans, sometimes called Australasians.

  Researchers described the Ust'-Ishim lineage as sitting "near trifurcation" between western and eastern Eurasian populations. Yet it shared a brief period of evolutionary drift with Eastern Eurasians in particular. It split from its ancestor shortly after that ancestor diverged from the Ancient Western Eurasians, represented by the Kostenki-14 specimen. Kostenki-14 remains the reference point against which that early split in the Ust'-Ishim lineage is still measured.