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Temporal genomic data hold great potential for studying evolutionary processes such as speciation. However, sampling across speciation events would, in many cases, require genomic time series that stretch well back into the Early Pleistocene subepoch. Although theoretical models suggest that DNA should survive on this timescale1, the oldest genomic data recovered so far are from a horse specimen dated to 780–560 thousand years ago2. Here we report the recovery of genome-wide data from three mammoth specimens dating to the Early and Middle Pleistocene subepochs, two of which are more than one million years old. We find that two distinct mammoth lineages were present in eastern Siberia during the Early Pleistocene. One of these lineages gave rise to the woolly mammoth and the other represents a previously unrecognized lineage that was ancestral to the first mammoths to colonize North America. Our analyses reveal that the Columbian mammoth of North America traces its ancestry to a Middle Pleistocene hybridization between these two lineages, with roughly equal admixture proportions. Finally, we show that the majority of protein-coding changes associated with cold adaptation in woolly mammoths were already present one million years ago. These findings highlight the potential of deep-time palaeogenomics to expand our understanding of speciation and long-term adaptive evolution. Siberian mammoth genomes from the Early and Middle Pleistocene subepochs reveal adaptive changes and a key hybridization event, highlighting the value of deep-time palaeogenomics for studies of speciation and long-term evolutionary trends.

The fossil record richly illustrates the origin of morphological adaptation through time. However, our understanding of the selective forces responsible in a given case, and the role of behaviour in the process, is hindered by assumptions of synchrony between environmental change, behavioural innovation and morphological response. Here I show, from independent proxy data through a 20-million-year sequence of fossil proboscideans in East Africa, that changes in environment, diet and morphology are often significantly offset chronologically, allowing dissection of the roles of behaviour and different selective drivers. These findings point the way to hypothesis-driven testing of the interplay between habitat change, behaviour and morphological adaptation with the use of independent proxies in the fossil record.

Body size reduction in mammals is usually associated with only moderate brain size reduction, because the brain and sensory organs complete their growth before the rest of the body during ontogeny. On this basis, 'phyletic dwarfs' are predicted to have a greater relative brain size than 'phyletic giants'. However, this trend has been questioned in the special case of dwarfism of mammals on islands. Here we show that the endocranial capacities of extinct dwarf species of hippopotamus from Madagascar are up to 30% smaller than those of a mainland African ancestor scaled to equivalent body mass. These results show that brain size reduction is much greater than predicted from an intraspecific 'late ontogenetic' model of dwarfism in which brain size scales to body size with an exponent of 0.35. The nature of the proportional change or grade shift observed here indicates that selective pressures on brain size are potentially independent of those on body size. This study demonstrates empirically that it is mechanistically possible for dwarf mammals on islands to evolve significantly smaller brains than would be predicted from a model of dwarfing based on the intraspecific scaling of the mainland ancestor. Our findings challenge current understanding of brain-body allometric relationships in mammals and suggest that the process of dwarfism could in principle explain small brain size, a factor relevant to the interpretation of the small-brained hominin found on the Island of Flores, Indonesia.

The giant deer, or 'Irish elk', has featured extensively in debates on adaptation, sexual selection, and extinction. Its huge antlers--the largest of any deer species, living or extinct--formed a focus of much past work. Yet the phylogenetic position of the giant deer has remained an enigma. On the basis of its flattened antlers, the species was previously regarded as closely related to the living fallow deer. Recent morphological studies, however, have challenged that view and placed the giant deer closer to the living red deer or wapiti. Here we present a new phylogenetic analysis encompassing morphological and DNA sequence evidence, and find that both sets of data independently support a sister-group relationship of giant and fallow deer. Our results include the successful extraction and sequencing of DNA from this extinct species, and highlight the value of a joint molecular and morphological approach.

Despite remarkable progress in the study of ancient DNA, the amount of continuous sequence retrievable from Late Pleistocene organisms is still limited. Segments of about 1,000 base pairs have been reconstructed for mammoths and a few other species, but that's often not much to go on when it comes to studying inter-species relationships. Now a new PCR-based method that makes clever use of sequence overlaps and multiple amplifications has made it possible to produce long DNA sequences from minute amounts of bone material. Starting from just 200 mg of bone, this method has generated the complete mitochondrial genome sequence of a Pleistocene woolly mammoth preserved in permafrost, a total of over 16,000 base pairs. The sequence resolves a long-standing controversy over mammoth phylogeny, showing the woolly mammoth to be more closely related to the Asian elephant than to its African cousin. In studying the genomes of extinct species, two principal limitations are typically the small quantities of endogenous ancient DNA and its degraded condition1, even though products of up to 1,600 base pairs (bp) have been amplified in rare cases2. Using small overlapping polymerase chain reaction products, longer stretches of sequences or even whole mitochondrial genomes3,4 can be reconstructed, but this approach is limited by the number of amplifications that can be performed from rare samples. Thus, even from well-studied Pleistocene species such as mammoths, ground sloths and cave bears, no DNA sequences of more than about 1,000 bp have been reconstructed5,6,7. Here we report the complete mitochondrial genome sequence of the Pleistocene woolly mammoth Mammuthus primigenius. We used about 200 mg of bone and a new approach that allows the simultaneous retrieval of multiple sequences from small amounts of degraded DNA. Our phylogenetic analyses show that the mammoth was more closely related to the Asian than to the African elephant. However, the divergence of mammoth, African and Asian elephants occurred over a short time, corresponding to only about 7% of the total length of the phylogenetic tree for the three evolutionary lineages.

A collection of stone tools from East Anglia has been dated at around 700,000 years old, making them the the earliest signs of human activity in northern Europe by about 200,000 years. Humans were present in sunnier southern Europe before 750,000 years ago, but until now there were no traces of human activity north of the Alps before half a million years ago. The flint artefacts found at Pakefield, near Lowestoft, extend human activity in Britain and the entire northern European landmass back to an antiquity we're more used to from southern Europe. The tools are from the well known Cromer Forest-bed Formation, which has yielded Ice Age fossils for over a century. But this find was notable as the 32 worked flints, including the scraper shown on the cover, were in a clearly datable stratigraphic context. Go to tinyurl.com/d2zko for video clips of the press conference announcing this discovery. The colonization of Eurasia by early humans is a key event after their spread out of Africa, but the nature, timing and ecological context of the earliest human occupation of northwest Europe is uncertain and has been the subject of intense debate1. The southern Caucasus was occupied about 1.8 million years (Myr) ago2, whereas human remains from Atapuerca-TD6, Spain (more than 780 kyr ago)3 and Ceprano, Italy (about 800 kyr ago)4 show that early Homo had dispersed to the Mediterranean hinterland before the Brunhes–Matuyama magnetic polarity reversal (780 kyr ago). Until now, the earliest uncontested artefacts from northern Europe were much younger, suggesting that humans were unable to colonize northern latitudes until about 500 kyr ago5,6. Here we report flint artefacts from the Cromer Forest-bed Formation at Pakefield (52° N), Suffolk, UK, from an interglacial sequence yielding a diverse range of plant and animal fossils. Event and lithostratigraphy, palaeomagnetism, amino acid geochronology and biostratigraphy indicate that the artefacts date to the early part of the Brunhes Chron (about 700 kyr ago) and thus represent the earliest unequivocal evidence for human presence north of the Alps.

The extinction of the many well-known large mammals (megafauna) of the Late Pleistocene epoch has usually been attributed to ‘overkill’ by human hunters, climatic/vegetational changes or to a combination of both1,2. An accurate knowledge of the geography and chronology of these extinctions is crucial for testing these hypotheses. Previous assumptions that the megafauna of northern Eurasia had disappeared by the Pleistocene/Holocene transition2 were first challenged a decade ago by the discovery that the latest woolly mammoths on Wrangel Island, northeastern Siberia, were contemporaneous with ancient Egyptian civilization3,4. Here we show that another spectacular megafaunal species, the giant deer or ‘Irish elk’, survived to around 6,900 radiocarbon yr bp (about 7,700 yr ago) in western Siberia—more than three millennia later than its previously accepted terminal date2,5—and therefore, that the reasons for its ultimate demise are to be sought in Holocene not Pleistocene events. Before their extinction, both giant deer and woolly mammoth underwent dramatic shifts in distribution, driven largely by climatic/vegetational changes. Their differing responses reflect major differences in ecology.

Giant deer on the Isle of Man around 9,000 years ago may have been the last of the line. The giant deer Megaloceros giganteus was a celebrated victim of the Late Pleistocene megafaunal extinction, the timing and causes of which are hotly debated1. Until now, it was believed that the giant deer's demise occurred during the Late Glacial (about 10,600 years ago), before the Pleistocene–Holocene boundary. Here we report new radiocarbon dates from two specimens in stratified contexts, which indicate that a giant deer population still existed around the northern Irish Sea Basin in the early Holocene — 1,400 years after their supposed extinction.

Were the Late Pleistocene extinctions of large mammals the result of climate change or big-game hunting by humans? Reconstructing the biology of extinct species provides clues to the answer.

When, where and why was the two-humped Bactrian camel first domesticated? A new analysis tackles these issues, drawing on a variety of archaeological evidence (and including discussion of a translation of a twelfth-century Chinese manual on camel husbandry). The answer to the first question remains pretty much a mystery. As to the second and third, the authors surmise that the likeliest answers are Kazakhstan, northern Mongolia or northern China, and for meat.

Fossil Horses: Systematics, Paleobiology and Evolution of the Family Equidae. By Bruce J. MacFadden. Cambridge University Press: 1993. Pp. 369. £45, $74.95.

THE dwarfing of large mammals on islands occurred repeatedly in the Pleistocene. Elephants, deer, hippopotami and other species became dwarfed on islands in Indonesia, the Mediterranean, the east Pacific and elsewhere1,2. In most cases, the full-sized ancestral form can be recognized among the adjacent mainland fauna, but evolutionary rates cannot be estimated because the entry of the ancestor onto the island, and appearance of the dwarf form, are poorly dated. Here I give the first example in which the island dwarf is well dated, the full-sized ancestor is found in demonstrably older deposits on the island, and a good estimate can be made for the duration of the isolation leading to dwarfing. In the Last Interglacial, red deer on Jersey, Channel Islands, became reduced to one sixth of their body weight in less than six thousand years.

We report the discovery of abundant skeletal remains of mammoth, Mammuthus primigenius (Blumenbach) from late-glacial sediments filling a kettle-hole near Shrewsbury, Shropshire in England. Radiocarbon dated to ˜ 12,800 yr BP, they are by far the latest dated remains of mammoth from Britain, extending its known occurrence there by around 5,000 yr. They provide clear evidence that the full-glacial episode of the last cold stage did not bring about the final extinction of the mammoth in western Europe, but that the species returned in the late glacial before its ultimate demise. The finds represent the most complete mammoths found in Britain, and include the largely complete skeleton of an adult together with partial skeletons of at least three juveniles.

Elephant Memories: Thirteen Years in the Life of an Elephant Family. By Cynthia Moss. Elm Tree Books, 27 Wrights Lane, London/William Morrow, New York: 1988. Pp.336. £15.95, $22.95.