Author Archives: jeronen

Dietary Change and Evolution of Horses in North America

Dietary Change and Evolution of Horses in North America
Matthew C. Mihlbachler, Florent Rivals, Nikos Solounias, Gina M. Semprebon

The evolution of high-crowned molars among horses (Family Equidae) is thought to be an adaptation for abrasive diets associated with the spread of grasslands. The sharpness and relief of the worn cusp apices of teeth (mesowear) are a measure of dietary abrasion. We collected mesowear data for North American Equidae for the past 55.5 million years to test the association of molar height and dietary abrasion. Mesowear trends in horses are reflective of global cooling and associated vegetation changes. There is a strong correlation between mesowear and crown height in horses; however, most horse paleopopulations had highly variable amounts of dietary abrasion, suggesting that selective pressures for crown height may have been weak much of the time. However, instances of higher abrasion were observed in some paleopopulations, suggesting intervals of stronger selection for the evolution of dentitions, including the early Miocene shortly before the first appearance of Equinae, the horse subfamily in which high-crowned dentitions evolved.

Science 4 March 2011:
Vol. 331 no. 6021 pp. 1178-1181
DOI: 10.1126/science.1196166

Has the Earth’s sixth mass extinction already arrived?

Has the Earth’s sixth mass extinction already arrived?

Anthony D. Barnosky, Nicholas Matzke, Susumu Tomiya, Guinevere O. U.Wogan, Brian Swartz, Tiago B. Quental,
Charles Marshall, Jenny L. McGuire, Emily L. Lindsey, Kaitlin C. Maguire, Ben Mersey & Elizabeth A. Ferrer

Palaeontologists characterize mass extinctions as times when the Earth loses more than three-quarters of its species in a geologically short interval, as has happened only five times in the past 540 million years or so. Biologists now suggest that a sixth mass extinction may be under way, given the known species losses over the past few centuries and millennia. Here we review how differences between fossil and modern data and the addition of recently available palaeontological information influence our understanding of the current extinction crisis. Our results confirm that current extinction rates are higher than would be expected from the fossil record, highlighting the need for effective conservation measures.

http://www.nature.com/nature/journal/v471/n7336/full/nature09678.html

Woolly mammoth (Mammuthus primigenius Blum.) and its environment in northern Europe during the last glaciation

Woolly mammoth (Mammuthus primigenius Blum.) and its environment in northern Europe during the last glaciation

P. Ukkonen, K. Aaris-Sørensen, L. Arppe, P.U. Clark, L. Daugnora, A.M. Lister, L. Lõugas, H. Seppä, R.S. Sommer, A.J. Stuart, P. Wojtal, I. Zupiņš

Quaternary Science Reviews
Volume 30, Issues 5-6, March 2011, Pages 693-712

Abstract

Woolly mammoths were large, herbivorous, cold-adapted mammals of the Late Pleistocene. The diet and habitat requirements of the species set certain constraints on the palaeoenvironments it could occupy. The relationship between the mammoth’s shifting range and changing environments can be explored using independent data on ice sheet configuration, temperature, and vegetation, provided the locality and age of the fossil remains can be validated. Here we present a comprehensive record of occurrence of the woolly mammoth in the circum-Baltic region of northern Europe during the last glaciation, based on a compilation of radiocarbon-dated remains. The record shows that the mammoth was widespread in northern and north-eastern Europe during Marine Isotope Stage 3 (MIS 3), at 50,000–30,000 calibrated years ago (50–30 ka). The presence of the species up to 65°N latitude supports the restriction of the Scandinavian Ice Sheet (SIS) during MIS 3. The widest distribution range round 30 ka was followed by a decline that led to the disappearance of mammoths from the area during the maximum extent of the SIS, from 22 to 18 ka. The woolly mammoth re-colonized the Baltic region and southern Scandinavia after the onset of the late-glacial deglaciation at 17 ka. The late-glacial record suggests a markedly fluctuating population changing its range in tune with the rapid environmental changes. The last appearance of mammoth in our study region was in Estonia during the Younger Dryas (Greenland Stadial 1; GS1) at about 12 ka. The two major periods of occurrence during MIS 3 and the late-glacial stadial suggest that mammoth had a wide tolerance of open to semi-open tundra and steppe-tundra habitats with intermediately cold climate, whereas the 22–18 ka disappearance suggests a major southward and/or eastward retreat in response to extremely cold, glacial conditions near the SIS margin. The final regional extinction correlates with the re-forestation during the rapid warming at the Younger Dryas–Holocene boundary.

How cold was it for Neanderthals moving to Central Europe during warm phases of the last glaciation?

Grzegorz Skrzypek, Andrzej Wiśniewski, Pauline F. Grierson
Quaternary Science Reviews
Volume 30, Issues 5-6, March 2011, Pages 481-487

Abstract

Precise estimates of mean annual temperature (MAT) for when Neanderthals occupied Central Europe are critical for understanding the role that climatic and associated environmental factors played in Neanderthal migrations and in their ultimate extinction. Neanderthals were continuously present in the relatively warm regions of southern and Western Europe in the Pleistocene but only temporarily settled Central Europe (CE), presumably because of its colder and less hospitable climate. Here, we present a new approach for more spatially and temporally accurate estimation of palaeotemperatures based on the stable oxygen isotope composition of phosphates extracted from animal teeth found at sites linked directly to concurrent Neanderthal occupation. We provide evidence that Neanderthals migrated along the Odra Valley of CE during warmer periods throughout the Upper Pleistocene. The MATs during these migrations were about 6.8 °C for the warm phase of Oxygen Isotope Stage OIS 5a–d (prior to the OIS4 cold event) at not, vert, similar115–74,000 yr BP and about 6.3 °C during the early OIS 3 warm phase not, vert, similar59–41,000 yr BP. Our results show that temperatures during these phases peaked 2–4 °C above longer term estimates from ice cores and pollen records. We argue that our approach can provide valuable insights into evaluating the role of climate in human migration patterns in the Pleistocene.

The Southern Route “Out of Africa”: Evidence for an Early Expansion of Modern Humans into Arabia

The Southern Route “Out of Africa”:
Evidence for an Early Expansion
of Modern Humans into Arabia

Simon J. Armitage,1 Sabah A. Jasim,2 Anthony E. Marks,3 Adrian G. Parker,4
Vitaly I. Usik,5 Hans-Peter Uerpmann6*

The timing of the dispersal of anatomically modern humans (AMH) out of Africa is a fundamental question in human evolutionary studies. Existing data suggest a rapid coastal exodus via the Indian Ocean rim around 60,000 years ago. We present evidence from Jebel Faya, United Arab Emirates, demonstrating human presence in eastern Arabia during the last interglacial. The tool kit found at Jebel Faya has affinities to the late Middle Stone Age in northeast Africa, indicating that technological innovation was not necessary to facilitate migration into Arabia. Instead, we propose that low eustatic sea level and increased rainfall during the transition between marine isotope stages 6 and 5 allowed humans to populate Arabia. This evidence implies that AMH may have been present in South Asia before the Toba eruption

Science 28 January 2011:
Vol. 331 no. 6016 pp. 453-456
DOI: 10.1126/science.1199113

See also a discussion paper in Nature:

Archaeology: Trailblazers across Arabia
Michael D. Petraglia
Nature
Volume
470,
50–51
(03 February 2011)
DOI: 10.1038/470050a