Literature Review: Human Paleontology

March 26, 2013 at 6:09 am (history (human), mammals, paleontology, Prehistoric Life series)
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by Carl Strang

This last post on the scientific literature from 2012 includes notes from studies that spanned the time range of human evolution and geographic expansion. The review begins 4 million years ago with Australopithecus anamensis in Africa, and ends a little over 10,000 years ago in Ohio.

Estebaranz, Ferran, et al. Buccal dental microwear analyses support greater specialization in consumption of hard foodstuffs for Australopithecus anamensis. Journal of Anthropological Sciences, 2012; 90: 1-24 DOI: 10.4436/jass.90006 As described in a ScienceDaily article. Microwear of molars is consistent with a diet of seeds, tubers and leaves for Australopithecus anamensis. This contrasts with the fruit-heavy diets of both the ancestor of anamensis (Ardepithecus ramidus) and its descendant Australopithecus afarensis.

Green, David J., and Zeresenay Alemseged. 2012. Australopithecus afarensis scapular ontogeny, function, and the role of climbing in human evolution. Science 338: 514-517. For the first time, shoulder blades of this species have been studied. Their similarity to those of apes (both in structure and in the fact that those of young are similar to those of adults) suggests that this upright walking species still was adapted for tree climbing as well.

Human use of fire may go back a million years.

Human use of fire may go back a million years.

Berna, Francesco, et al. Microstratigraphic evidence of in situ fire in the Acheulean strata of Wonderwerk Cave, Northern Cape province, South Africa. Proceedings of the National Academy of Sciences, April 2, 2012 DOI: 10.1073/pnas.1117620109 They found evidence of cultural use of fire dated 1 million years ago, 300,000 years earlier than the previous evidence. This was the time of Homo erectus.

Wilkins, Jayne, Benjamin J. Schoville, Kyle S. Brown, and Michael Chazan. 2012. Evidence for early hafted hunting technology. Science 338:942-946. They found spear points in South Africa from 500,000 years ago, the time of Homo heidelbergensis, the last common ancestor of Neanderthals and modern humans. This indicates that the spears used by both had a common cultural origin. The previous known oldest spears were at 300,000 years ago.

Mathias RA, Fu W, Akey JM, Ainsworth HC, Torgerson DG, et al. (2012) Adaptive Evolution of the FADS Gene Cluster within Africa. PLoS ONE 7(9): e44926. doi:10.1371/journal.pone.0044926 They looked at genes which make possible the conversion of medium-length fatty acids from plants into longer-chain fatty acids essential for human brain function. Variation in human populations and in relation to chimpanzees points to the fixation of these gene variations around 85,000 years ago. This coincides with the time when humans began to expand through Africa away from limited coastal areas, where they had remained for the first 100,000 years of the species’ existence. The authors suggest that prior to this mutational event, humans needed fish and aquatic invertebrates to provide these fatty acids, but afterwards could live in a broader range of environments by including plants in the diet that provided the precursors for the brain chemicals. A ScienceDaily article describing this study points out that African Americans as well as Africans, who have the highest functionality of these genes, more often suffer the side effects of hypertension, coronary artery disease, and other consequences of too-efficient use of vegetable oils in cooking.

Finlayson, C., et al. (2012) Birds of a Feather: Neanderthal Exploitation of Raptors and Corvids. PLoS ONE 7(9): e45927. doi:10.1371/journal.pone.0045927 They studied remains in a number of caves and other Neanderthal sites over a long span of time, and found evidence that Neanderthals commonly and deliberately, removed corvid and raptor flight feathers, apparently for use in symbolic adornment.

Rule, Susan, et al. 2012. The aftermath of megafaunal extinction: ecosystem transformation in Pleistocene Australia. Science 335:1483-1486. They used charcoal as an indicator of human activity, a fungal dung spore for megafauna, and also looked at changes in plant communities as indicated by pollen in core samples over a time span from 130,000 to 24,000 years ago. They conclude that human hunting was responsible for Australian megafauna extinctions (at least 20 genera of marsupials, monotremes, birds and reptiles). They then argue that the timing of vegetation changes points to the loss of megafauna leading to an increase in grasses and other fine fuels, so that resulting wildfires promoted a vegetation change in the region around the cored swamp in northeast Australia, from a mixed rainforest to a desert shrub-grass ecosystem.

Human use of fire may go back a million years.

Reconstructed ground sloth

Brian G. Redmond, H Gregory McDonald, Haskel J. Greenfield, Matthew L. Burr. New evidence for Late Pleistocene human exploitation of Jefferson’s Ground Sloth (Megalonyx jeffersonii) from northern Ohio, USA. World Archaeology, 2012; 44 (1): 75 DOI: 10.1080/00438243.2012.647576 A fossil thigh bone shows saw marks from stone tools were used to filet the muscle, 13,435-13,738 years ago.

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Literature Review: The Cenozoic Era

March 20, 2013 at 6:05 am (birds, botany, ecology, geology, paleontology, Prehistoric Life series)
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by Carl Strang

This week we look at some recent studies of the time between the Mesozoic Era and the present day. In recent years there has been much interest in the dynamics of climate change across the ages of the Earth.

A huge amount of carbon today is sequestered in the permafrost soils of the North.

A huge amount of carbon today is sequestered in the permafrost soils of the North.

Robert M. DeConto, et al. Past extreme warming events linked to massive carbon release from thawing permafrost. Nature, 2012; 484 (7392): 87 DOI: 10.1038/nature10929 They combined modeling with the Earth’s orbital dynamics to show the likelihood that in the Paleocene, when the Earth’s orbit became more eccentric and tilt became greater, this resulted in thawing and decomposition of permafrost, releasing huge amounts of carbon dioxide and resulting in a positive feedback loop that produced the Paleocene-Eocene Thermal Maximum.

Pitcher plants, Big Thicket. The following study traces their origin.

Pitcher plants, Big Thicket. The following study traces their origin.

Ellison AM, et al. (2012) Phylogeny and Biogeography of the Carnivorous Plant Family Sarraceniaceae. PLoS ONE 7(6): e39291. doi:10.1371/journal.pone.0039291 They studied nuclear, mitochondrial and plasmid genes to sort out relationships and evolutionary history of the pitcher plants. They conclude that the family appeared in South America 44-53mya (million years ago, Eocene), and by the end of the Eocene was widespread in North and South America.

G. Grellet-Tinner, et al. (2012) The First Occurrence in the Fossil Record of an Aquatic Avian Twig-Nest with Phoenicopteriformes Eggs: Evolutionary Implications. PLoS ONE 7(10): e46972. doi:10.1371/journal.pone.0046972 They found fossils of a basal flamingo in association with eggshells and a floating nest that are like those of modern grebes, in an early Miocene shallow-lake wetland with high evaporation, in Spain. Though they agree that there was an earlier split between the grebes and the flamingos, they mention that fossil flamingos are known from the Oligocene, grebes from the Miocene. Apparently the bones are insufficient to provide much of an understanding of this early flamingo’s appearance.

Zhang Z, Feduccia A, James HF (2012) A Late Miocene Accipitrid (Aves: Accipitriformes) from Nebraska and Its Implications for the Divergence of Old World Vultures. PLoS ONE 7(11): e48842. doi:10.1371/journal.pone.0048842 They describe a fossil bird from Nebraska that links New World hawks and eagles to the Gypaetinae, one of the subfamilies of Old World vultures. This places the timing of that group’s origin in the Miocene, and supports its evolutionary separation from the other Old World vulture subfamily, the Aegypiinae.

Elderfield, H., et al. 2012. Evolution of ocean temperature and ice volume through the mid-Pleistocene climate transition. Science 337:704-709. (Comment by Peter U. Clark on pp. 656-658 in the same issue). They sorted through various isotopic proxies in marine sediments from New Zealand, and found an association between the mysterious change in ice age periodicity around 900,000 years ago (from cycles of 41,000 years to the more recent cycles of 100,000 years, a change not connected to the Earth orbit fluctuations now known to be the underlying cause of ice age cycling generally) and an increase in the volume of ice around Antarctica. They suggest that “an anomalously low Southern Hemisphere summer insolation” failed to melt the Antarctic ice during one interglacial period, and that the ice added during the following ice age was enough to produce the observed period change. The sea level drop during ice ages changed from 70 meters to 120 meters as a result. Their data also argue against a gradual cooling, from changes in atmospheric carbon dioxide, as the primary driver of the periodicity change.

Jeremy D. Shakun, et al. Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation. Nature, 2012; 484 (7392): 49 DOI: 10.1038/nature10915 From an article in ScienceDaily: “Here is what the researchers think happened.

“Small changes in Earth’s orbit around the sun affected the amount of sunlight striking the northern hemisphere, melting ice sheets that covered Canada and Europe. That fresh water flowed off of the continent into the Atlantic Ocean, where it formed a lid over the sinking end of the Atlantic Meridional Overturning Circulation — a part of a global network of currents that brings warm water up from the tropics and today keeps Europe temperate despite its high latitudes.

“The ocean circulation warms the northern hemisphere at the expense of the south, the researchers say, but when the fresh water draining off the continent at the end of the last Ice Age entered the North Atlantic, it essentially put the brakes on the current and disrupted the delivery of heat to the northern latitudes.

“ʻWhen the heat transport stops, it cools the north and heat builds up in the Southern Hemisphere,ʼ Shakun said. ʻThe Antarctic would have warmed rapidly, much faster than the time it takes to get CO2 out of the deep sea, where it was likely stored.

“ʻThe warming of the Southern Ocean may have shifted the winds as well as melted sea ice, and eventually drawn the CO2 out of the deep water, and released it into the atmosphere,ʼ Shakun said. ʻThat, in turn, would have amplified warming on a global scale.ʼ”

The study was a global review of the timing of temperature and atmospheric carbon dioxide changes at the end of the last period of continental glaciation.

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Literature Review: Mesozoic Era

March 13, 2013 at 6:08 am (birds, ecology, mammals, paleontology, Prehistoric Life series, reptiles and amphibians)
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by Carl Strang

This week’s scientific literature focus is on recent studies of the Mesozoic Era, the “age of dinosaurs.”

Sun,Yadong, et al. 2012. Lethally Hot Temperatures During the Early Triassic Greenhouse. Science 338: 366-370. They used oxygen isotope ratios in conodont (small eel-like fishes) teeth to measure temperatures, and found that for 5 million years into the Triassic, temperatures were too high to permit terrestrial or marine vertebrate life in the tropics (50-60C = 122-140F on land, 40C = 104F ocean surface waters). Some ferns and shrubs could withstand this but their growth was limited, and there were no tropical forests. Without plants to sequester carbon dioxide, the runaway global warming resulted. Until this study it was thought that ocean temperatures could not exceed 30C.

Artist’s rendition of a prosauropod, subject of the following study, from an exhibit at the Field Museum of Natural History.

Artist’s rendition of a prosauropod, subject of the following study, from an exhibit at the Field Museum of Natural History.

Robert R. Reisz, David C. Evans, Eric M. Roberts, Hans-Dieter Sues, Adam M. Yates. Oldest known dinosaurian nesting site and reproductive biology of the Early Jurassic sauropodomorph Massospondylus. Proceedings of the National Academy of Sciences, 2012; DOI: 10.1073/pnas.1109385109 The grouped nests, eggs showing embryo details, and the presence of tracks of young twice the size of the embryos, points to a prolonged attachment to the nest sites. The eggs in the nests appear to have been carefully arranged by the adults. All of this points to prolonged parental care in a relatively early (prosauropod) dinosaur.

Balter, Michael. 2012. Flying dinos and baby birds offer new clues about how avians took wing. Science 338:591-592. This news review article discusses the origin of flight in dinosaurs and birds, focusing on Microraptor, a crow-sized Chinese dromaeosaurid. There has been some debate about this and other “4-winged” species which had wing-like rows of quill feathers on their legs as well as their forelimbs. An early idea was that the leg structures added gliding planes to those of the wings. Others argue that they would have served as rudders for quick turns, aided by stabilization from the animal’s long tail. Another idea with traction among many in this field is the “wing-assisted incline running” hypothesis, according to which the wings would have helped such animals quickly to climb trees to escape predators. Some recent research has focused on immature chukars, birds which have a number of features in common with the feathered dinosaurs but which are lost during development as they are transformed into the adult birds’ structures. The immature chukars cannot fly, but they are able to perform wing-assisted incline running. They lose much of this ability if their wing feathers are clipped.

Zelenitsky, Darla K., et al. 2012. Feathered non-avian dinosaurs from North America provide insight into wing origins. Science 338:510-514. The first fossil dinosaurs with feathers found in North America are ornithomimids from the Upper Cretaceous in which the young have only downy body coverings but adults add wings. These animals could not fly, so the quills were involved in adult activity such as courtship or brooding of young.

Achim G. Reisdorf, Michael Wuttke. Re-evaluating Moodie’s Opisthotonic-Posture Hypothesis in Fossil Vertebrates Part I: Reptiles—the taphonomy of the bipedal dinosaurs Compsognathus longipes and Juravenator starki from the Solnhofen Archipelago (Jurassic, Germany). Palaeobiodiversity and Palaeoenvironments, 2012; DOI: 10.1007/s12549-011-0068-y As described in a ScienceDaily article. Dinosaurs and relatives, including Archaeopteryx, often are found fossilized with the neck dramatically bent backward over the back. This had been thought to be a sort of death throes pattern, but Reisdorf and Wittke did experiments with chickens that revealed this to be a process of decomposition. A relatively decay-resistant ligament, the Ligamentum elasticum, is “pre-loaded” as a spring-like support along the top of the vertebral column in dinosaurs with long necks and tails. As decomposition proceeds in water (usually fossilized animals are preserved in aquatic sediments), the opposing muscles and connective tissues on the front of the neck break down first, so that the Ligamentum elasticum gradually pulls the neck back into the observed posture.

Gregory P. Wilson, Alistair R. Evans, Ian J. Corfe, Peter D. Smits, Mikael Fortelius, Jukka Jernvall. Adaptive radiation of multituberculate mammals before the extinction of dinosaurs. Nature, 2012; DOI: 10.1038/nature10880 From ScienceDaily article. They did a comparative study of multituberculates, an early mammal group that arose by 170mya (million years ago) and went extinct around 34mya. Their appearance as mouse-sized species preceded the diversification of angiosperms, but their own diversity increased after that happened, so that they ranged as large as beavers. There was a concurrent increase in tooth complexity, showing many facets facing in various directions especially in the molars, a change associated with a vegetarian diet (though many species had teeth more suggestive of an insect diet). Dinosaurs never matched this, even herbivorous ones either developing batteries of relatively flat-topped grinders, or swallowing plant material whole and using gastric mills. The small body size and dietary capabilities apparently contributed to multituberculate survival when the dinosaurs became extinct.

A model of a hadrosaur, Brookfield Zoo. These possibly hold the all-time record for tooth tissue complexity.

A model of a hadrosaur, Brookfield Zoo. These possibly hold the all-time record for tooth tissue complexity.

G. M. Erickson, Gregory M., et al. 2012. Complex dental structure and wear biomechanics in hadrosaurid dinosaurs. Science 338: 98-101. They examined the microstructure and mechanical properties of hadrosaur teeth, and found that these were more complex than molars of mammalian herbivores (with 6 rather than 4 tissue types), and were more effective as grinders of tough plant tissues. This helps explain why they became so successful, diverse and abundant in their time.

Gates TA, Prieto-Márquez A, Zanno LE (2012) Mountain Building Triggered Late Cretaceous North American Megaherbivore Dinosaur Radiation. PLoS ONE 7(8): e42135. doi:10.1371/journal.pone.0042135 They tie the unusual diversification of hadrosaurs and ceratopsians in western North America to the timing of its isolation by the inland seaway and the simultaneous development of 2 mountain ranges within it. This produced geographic isolation of populations over a large north-to-south gradient. They conclude that this was a special case, and it should not be assumed that such species diversity was characteristic of that time globally.

Stephen L. Brusatte, Richard J. Butler, Albert Prieto-Márquez, Mark A. Norell. Dinosaur morphological diversity and the end-Cretaceous extinction. Nature Communications, 2012; 3: 804 DOI: 10.1038/ncomms1815 As described in a ScienceDaily article. They reviewed morphological variation in the late Cretaceous in different parts of the world, working out of the premise that little variation may signal species headed toward extinction, while much variation may represent vigor and the potential for division into more species. Some groups in some parts of the world were found to represent each of these alternatives. Western North American dinosaurs after the incursion of the inland sea showed signs of deterioration. This may be tied to their more limited geographic area, the sea taking some land and western mountains further limiting the range. Large herbivores (hadrosaurs and ceratopsids) for the most part were declining, though carnivores and mid-sized herbivores (ankylosaurs, pachycephalosaurs) as well as sauropods were not. Asian hadrosaurs showed the opposite pattern, however.

Kerr, Richard A. 2012. Before the dinosaurs’ demise, a clambake extinction? Science 337:1280. News article describing a study of relatively thick strata from Antarctica that allow separation of effects of the Deccan Traps volcanic eruptions (comparable to the Siberian Traps associated with the end-Permian extinctions) from the impact that is generally regarded as ending the Cretaceous. The research group led by Thomas Tobin found results indicating that the Deccan Traps eruptions began 200,000 years before the impact, and this correlated with a warming of water in the bottom of the ocean and extinctions of clams and snails. Free-swimming ammonites were not affected by this, however.

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Literature Review: The Early Earth

March 6, 2013 at 6:54 am (botany, ecology, geology, invertebrates (other), paleontology, Prehistoric Life series)
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by Carl Strang

This week’s literature review begins a 4-week series that updates the material I shared in the Prehistoric Life winter series a couple years ago. The studies highlighted below looked at the time period from the Earth’s origin through the Paleozoic Era.

M. Touboul, I. S. Puchtel, R. J. Walker. 182W Evidence for Long-Term Preservation of Early Mantle Differentiation Products. Science, 2012; DOI: 10.1126/science.1216351

As described in a ScienceDaily article. They found evidence, in the form of a high portion of a particular tungsten isotope in some volcanic rocks, that a portion of the Earth’s previously formed mantle survived the Theia impact intact, implying that the Earth did not completely melt during or after that event. (This was the collision that in one dramatic moment created our moon and tilted the Earth on its axis, so that the seasons and the tides, so important to the diversity of life on Earth, became possible.)

 

Alexander, C.M.O’D., et al. 2012. The provenances of asteroids, and their contributions to the volatile inventories of the terrestrial planets. Science 337:721-723.

They looked at isotopic ratios of elements in asteroids vs. comets, and concluded that most of the water, nitrogen and carbon in the Earth and other inner planets came from bombardment by meteorites that originated as asteroids, rather than from comets.

 

M. R. Smith. Mouthparts of the Burgess Shale fossils Odontogriphus and Wiwaxia: implications for the ancestral molluscan radula. Proceedings of the Royal Society B: Biological Sciences, 2012; DOI: 10.1098/rspb.2012.1577

As reported in a ScienceDaily article. Graduate student Martin Smith examined fossils with a new form of electron microscopy, and found mouthparts that are clear predecessors of the molluscan radula. That early, tonguelike feature likely was used for scooping food from muddy sea floors rather than for scraping as radulas do today.

The following study points to green algae as the ancestors of all the land plants.

The following study points to green algae as the ancestors of all the land plants.

Timme RE, Bachvaroff TR, Delwiche CF (2012) Broad Phylogenomic Sampling and the Sister Lineage of Land Plants. PLoS ONE 7(1): e29696. doi:10.1371/journal.pone.0029696

They constructed a comparison of 160 nuclear genes to identify which group of algae contains the ancestral species which invaded land and became the founding species from which all land plants evolved. Their results point to the Zygnematales, the pond scum algae group.

 

Timothy M. Lenton, Michael Crouch, Martin Johnson, Nuno Pires & Liam Dolan. First plants cooled the Ordovician. Nature Geoscience, 2012 DOI: 10.1038/ngeo1390

From ScienceDaily. Their experiments on the chemical weathering of rocks by mosses suggest that the invasion of land plants released minerals that took carbon dioxide out of the atmosphere, and also stimulated oceanic blooms that further sequestered carbon as the resulting organisms were buried, in addition to the carbon sequestered by the land plants themselves. The authors estimate that the resulting carbon dioxide depletion was sufficient to trigger the end-Ordovician ice ages and associated extinctions. They also point out that plants continue to have a cooling effect on the atmosphere, though in the present day this is overwhelmed by technological injection of carbon dioxide.

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Lessons from Travels: Caribou

February 7, 2013 at 6:56 am (Lessons from Travels, mammals, paleontology)
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by Carl Strang

Travel offers many comparisons to the home landscape. Sometimes you can go back in time. I felt that way during my trip to Newfoundland in 2002, when my first day’s drive brought me to a herd of caribou.

The irregular southeastern peninsula of this island province in Canada offers the rare opportunity to encounter caribou along a paved road.

The irregular southeastern peninsula of this island province in Canada offers the rare opportunity to encounter caribou along a paved road.

A curious calf detached itself from the group and approached my stopped car.

My clicking shutter sent him back to the herd.

My clicking shutter sent him back to the herd.

Thousands of years before paved roads, as the glacier retreated from northeast Illinois, caribou followed with the tundra and stunted early trees as they trailed the ice edge.

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Literature Review: Earliest Animal Life

November 20, 2012 at 7:10 am (ecology, geology, invertebrates (other), paleontology)
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by Carl Strang

Yesterday’s post featured reef communities of today and the distant past. Today I want to stay in those early times when multicellular animals first entered the fossil record. The first paper was published about a year ago in Science.

Erwin, Douglas H., et al. 2011. The Cambrian conundrum: early divergence and later ecological success in the early history of animals. Science 334:1091-1097.

They used a variety of improved molecular clock, fossil, developmental and ecological data to look at animal diversification which seemed to appear full blown in the Cambrian Period at the beginning of the Paleozoic Era. They concluded “that the major animal clades diverged many tens of millions of years before their first appearance in the fossil record,” with basic developmental toolkits appearing in the Cryogenian Period of the Proterozoic Eon (before that eon’s final, Ediacaran Period). The researchers place the split between sponges and other animals in the mid-Cryogenian about 750 million years ago (mya), with Cnidaria (the group that today includes corals, sea anemones and jellyfish) appearing around 700mya, Chordates around the beginning of the Ediacaran, arthropods around the beginning of the Cambrian, and vertebrates in the late Cambrian. Only some of the well-known fossil Ediacaran organisms can be tentatively tied to the animals of today: some possible sponges, mollusks and placozoa. Otherwise, there are only some suggestive trace fossils (e.g., burrows) from the Ediacaran Period that point to metazoan animals. Erwin’s group attributes the apparent “Cambrian explosion” to the evolution of predation, which applied selective pressure resulting in protective shells and other structures that were better preserved in the fossil record.

Barnacles, arthropods that protect themselves with shells.

Another paper, published earlier this year, added another dimension to the story.

Shanan E. Peters, Robert R. Gaines. Formation of the ‘Great Unconformity’ as a trigger for the Cambrian explosion. Nature, 2012; 484 (7394): 363 DOI: 10.1038/nature10969

As reported in a ScienceDaily article. This study focused on the largest gap in the geologic record worldwide, dividing the Proterozoic Eon from the Cambrian Period which opened the Paleozoic Era, and tied that unconformity to a hypothesis about the sudden appearance of diverse life forms and skeletal features. They suggest that the erosion of preCambrian rock that produced the unconformity had the effect of adding concentrations of dissolved minerals to the sea. The resulting altered chemistry of their environment posed a challenge to living forms. The first production of biominerals thus was to remove those substances from organisms’ tissues. Having evolved that capability, animals then had the foundation for evolution of various uses of those minerals in shells and other skeletal formations, teeth, etc.

Thus the geological processes that grew the early continents, and lifted them above the sea, altered the chemistry of that sea. There were no land plants to resist the erosion. The marine animals, in addressing the challenge posed by the increased mineral content, found ways to create hard parts which in some were useful tools for predation, and in others were armor to resist that predation. The visible result of this biological arms race was the “Cambrian explosion,” in which multicellular life forms suddenly began to appear as fossils. But now evidence exists that points to those animals’ ancestors having diversified much much earlier.

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Lessons from Travels: Reefs

November 19, 2012 at 7:23 am (fishes, geology, invertebrates (other), Lessons from Travels, paleontology)
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by Carl Strang

One of the most breathtaking experiences is that of tropical coral reefs. Whether you explore them by snorkeling, as I have done a few times, or take the plunge and scuba dive, the beauty of reef communities is so far removed from our everyday experience that it safely can be described as “out of this world.”

The shapes and colors of the corals and other fixed life forms are sufficient to satisfy the aesthetic need. But then add the diverse, colorful fishes and other freely moving animals, and the experience is transporting.

Beaches near reefs may be filled with the rubble from eroded coral formations, as well as mollusk shells and other remains of ocean life.

The pieces are reminiscent of fossils.

This brings us back home. Our bedrock in northeast Illinois and northwest Indiana is Paleozoic in age. It formed when our part of the world was a shallow sea, and was in fact punctuated by reef communities. There were corals, though they were not the ancestors of today’s corals. For most of that time fishes were absent or few. I think, though, that snorkeling or diving in those reefs would have been just as transfixing as today’s experience. The trilobites and other animals were diverse and active, some swam, and they well may have been as colorful and patterned as the reef animals of today.

Winter is edging in, and so we enter the season when tropical reefs seem most remote in time and space. One brief respite can be found in the prehistoric life exhibit at Chicago’s Field Museum of Natural History. There is an enormous animated wall that shows what a Cambrian reef might have been like, with the fixed forms, the slowly moving ones, the fast swimmers, the episodes of predation, all with a very relaxing background sound. I cannot visit that museum without spending a few minutes enjoying that scene. Sometimes lessons don’t need distant travel.

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Lessons from Travels: Peat Soils

November 1, 2012 at 6:10 am (botany, ecology, Lessons from Travels, mammals, paleontology)
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by Carl Strang

With November’s arrival, this blog shifts to its winter mode. I will be bringing in posts that share comments on the year’s scientific literature that are relevant to local natural history. There also will be more species dossiers. Of course, ongoing observations from the present season will continue to appear. Finally, there will be weekly episodes in the winter series. Past winter series have focused on science and spirituality (the Winter Campfire) and prehistoric life. This winter I will continue, and perhaps conclude, the Lessons from Travels series I began last year. The idea is to draw upon comparisons between northeastern Illinois and other parts of the world which cast a light on our local ecology and natural history.

A few years ago the Forest Preserve District of DuPage County collaborated with Chicago’s Field Museum of Natural History to conduct a paleontological dig at Pratts Wayne Woods Forest Preserve. Some mastodon molar teeth and bone fragments had been found at the site, and we brought in high school teachers and students to excavate parts of the site.

Here the digging began, 2007. Note the marsh in the background.

The dig went for two seasons. We mainly found fragments of the mastodon’s tusks. During the second year we uncovered some buried black spruce trees.

The stem of one of the trees runs the length of this trench.

The spruces were there when the mastodon died. That tree species no longer occurs in Illinois, though it is common in the North, where it retreated in the wake of the melting glacier. As we dug, we encountered buried soils that were familiar to me.

Buried peat soil.

This was exactly like soils we found when we dug into the permafrost in western Alaska, where I lived for several summers conducting my thesis research on glaucous gulls. Today there is much concern about the amount of carbon dioxide, and perhaps methane as well, that will be added to the atmosphere as climate change melts the permafrost. It seems that tundra fires will be major news in the future. At least then, maybe people will be able to bury their dead.

This scene, fitting with Halloween just past, is from an abandoned village site in western Alaska. The powerful churning of the surface soil as it thaws and freezes each year prevents burials.

We were not able to complete the mastodon dig. We suspect that the major bones remain beneath that marsh. The Field Museum withdrew from the project, and keeping even a small portion of the marsh pumped out for digging is more difficult and expensive than anyone wishes to pursue (though who knows, if we continue to have droughts like this past summer, it may become a practical possibility). For now the buried peat soils, the tree stems we left in place and covered, and the remainder of the mastodon, wait patiently as they have done for thousands of years.

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Literature Review: Pleistocene

April 2, 2012 at 6:20 am (archeology, mammals, paleontology, Prehistoric Life series)
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by Carl Strang

The following notes complete my review of last year’s scientific literature. These studies looked at the most recent epoch, the Pleistocene, and focus on the megafauna, the large mammals.

Mastodon fossil, an iconic megafaunal species

Edwards, Ceiridwen J., et al. Ancient Hybridization and an Irish Origin for the Modern Polar Bear Matriline. Current Biology, 07 July 2011 DOI: 10.1016/j.cub.2011.05.058     As described in a ScienceDaily article. This new mitochondrial DNA study places the female ancestor of all current polar bears in Ireland 50,000 years ago, at the peak of the last ice age. Brown and polar bears once were both circumpolar, or nearly so, and the ebb and flow of the glaciers brought them in and out of contact, providing hybridization opportunities. The authors mention that this continues today, with the retreat of polar ice bringing the two species more into contact, and several recent hybrid individuals are known. The researchers indicate that this process needs to be taken into consideration both in understanding the nature of these species and in conservation planning.

Long, Charles A., and Christopher J. Yahnke. 2011. End of the Pleistocene: elk-moose (Cervalces) and caribou (Rangifer) in Wisconsin. J. Mammal. 92:1127-1135. They describe the northernmost caribou fossils found to date in Wisconsin, from Marathon County. The Cervalces (also known as stag moose) from the same site is the first for the state, and northernmost for the species. The study location was at the boundary between the glacier’s Green Bay Lobe and the driftless area. The age of the caribou antler is placed at 11,260-11,170 years ago. The elk-moose was from 12,920-12,790 years ago. The caribou probably was of the more southern woodland caribou species. The older elk-moose fossil was found in a sediment layer suggesting it lived close to the edge of the glacier, in more of a tundra environment.

Eline D. Lorenzen, et al. Species-specific responses of Late Quaternary megafauna to climate and humans. Nature, 2011; DOI: 10.1038/nature10574     As described in a ScienceDaily article. They looked at a range of genetic, archeological and other evidence, and found that the megafauna that went extinct and those that survived in the northern hemisphere represent a complex picture. All had survived previous glacial cycles by finding refugia in warm periods, with populations just large enough to continue. Some were able to do so again after the most recent glacial retreat, for instance caribou and musk oxen in the far north and bison in the North American plains, and survive to this day. Others did not, and in at least most of these cases humans are implicated, either by preventing retreat to refugia or by decimating the reduced populations.

Waters, Michael R., et al. 2011. Pre-Clovis mastodon hunting 13,800 years ago at the Manis site, Washington. Science 334:351-353. (also interpreted in a news article on p. 302 of the same issue). They found a spear point made of mastodon bone, imbedded in the rib of an adult male mastodon. It is dated to several hundred years before the Clovis culture. The location near the coast in Washington State is consistent with a coastal spread of people from Beringia, where bone spear points also were used. This also supports an extended period of megafauna hunting, further pointing toward human hunting as a factor in extinctions (a long period of hunting, even if it only removes animals slightly faster than they can reproduce, increases the importance of that mortality factor).

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Literature Review: Cenozoic Prior to Pleistocene

March 26, 2012 at 6:03 am (birds, botany, mammals, paleontology, plant-eating insects, Prehistoric Life series)
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by Carl Strang

The Cenozoic Era extends from the catastrophe that ended the Mesozoic Era up to the present day. Today’s literature review includes some research published last year pertaining to the bulk of the Cenozoic. Next week I will finish with some Pleistocene studies.

Leaf mine

Winkler, Isaac S., Conrad C. Labandeira, Torsten Wappler, and Peter Wilf. 2010. Distinguishing Agromyzidae (Diptera) leaf mines in the fossil record: new taxa from the Paleogene of North America and Germany and their evolutionary implications. J. Paleont. 84:935-954. Leaf-mining flies’ “mines often can be distinguished from those of other insects by the presence of an intermittent, fluidized frass trail that may alternate between the sides of the mine.” These researchers found an example of this pattern in an early Paleocene fossil sycamore leaf, Platanus raynoldsii, from Montana. They also see in those leaves “associated stereotypical marks identical to damage caused by feeding punctures of extant adult female Agromyzidae prior to oviposition.” This is the earliest fossil agromyzid (the family of these leaf-mining flies), named Phytomyzites biliapchaensis. Sycamores today do not have leaf mining agromyzids. The researchers speculate that this was “an evolutionary, possibly opportunistic colonization in the midst of the ecological chaos following the end-Cretaceous event in North America.”

Antoine, P.-O., et al. Middle Eocene rodents from Peruvian Amazonia reveal the pattern and timing of caviomorph origins and biogeography. Proceedings of the Royal Society B: Biological Sciences, 2011; DOI: 10.1098/rspb.2011.1732     Caviomorph rodents are the group that today characterizes the South American fauna and includes such species as guinea pigs and capybaras. These researchers found fossils of 3 species from 40 million years ago, much older than the previously known earliest South American rodents. The fossils indicate that the origin of that continent’s rodents was a rafting colonization from Africa.

Clarke, Julia A., et al. 2010. Fossil evidence for evolution of the shape and color of penguin feathers. Science 330:954-7. They describe a fossil giant penguin (Inkayacu paracasensis) from Peru, 36 million years ago in the late Eocene Epoch. The penguin’s primary wing feathers were difficult to distinguish from the coverts. Body contour feather shafts were broad like those of today’s penguins, and of similar proportionate length. Melanosomes suggest the colors were gray and reddish-brown.

Mihlbachler, Matthew C., et al. 2011. Dietary change and evolution of horses in North America. Science 331:1178-1181. They measured crown height and microwear of horse molars from the early Eocene on. There was considerable variation in the amount of wear for a given crown height, but in general wear increased with height. They interpret this to mean that selective pressure for increasing crown height generally was weak. There were times, however, when wear was greater, “including the early Miocene shortly before the first appearance of Equinae, the horse subfamily in which high-crowned dentitions evolved.” This supports the connection between the spread of grasslands in the Miocene (grasses are a relatively abrasive food) and the evolution of high-crowned teeth.

Cycad, King’s Canyon, central Australia.

Nagalingum, N.S., et al. 2011. Recent synchronous radiation of a living fossil. Science 334:796-799. They looked at cycad relationships based on molecular comparisons with fossil calibrations. The earlier assumption was that today’s 300 species are a holdover that survived the large drop in diversity in the Jurassic and Cretaceous that occurred with the rise in flowering plants, and thus are “living fossils.” Surprisingly this research group found that today’s species are the result of a diversification that began in the late Miocene, so that they “are not much older than ~12 million years.”

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