Megalodon and great white shark updates


Megalodon extinction timeline, credit: Robert Boessenecker

From the University of Wisconsin Oshkosh in the USA:

Giant ‘megalodon‘ shark extinct earlier than previously thought

Prehistoric beast not killed off by a supernova

February 13, 2019

Summary: ‘Megalodon‘ — a giant predatory shark that has inspired numerous documentaries, books and blockbuster movies — likely went extinct at least one million years earlier than previously thought, according to new research. This is a substantial adjustment as it means that O. megalodon likely went extinct long before a suite of strange seals, walruses, sea cows, porpoises, dolphins and whales all disappeared sometime about 1-2.5 million years ago.

Megalodon — a giant predatory shark that has inspired numerous documentaries, books and blockbuster movies — likely went extinct at least one million years earlier than previously thought, according to new research published Feb. 13 in PeerJ — the Journal of Life and Environmental Sciences.

Earlier research, which used a worldwide sample of fossils, suggested that the 50-foot-long, giant shark Otodus megalodon went extinct 2.6 million years ago. Another recent study attempted to link this extinction (and that of other marine species) with a supernova known to have occurred at about this time.

However, a team of researchers led by vertebrate paleontologist Robert Boessenecker with the College of Charleston, Charleston, South Carolina, noted that in many places there were problems with the data regarding individual fossils in the study estimating the extinction date.

In the new study, the researchers reported every fossil occurrence of O. megalodon from the densely sampled rock record of California and Baja California (Mexico) in order to estimate the extinction.

Besides Boessenecker, the research team included Dana Ehret, of New Jersey State Museum; Douglas Long, of the California Academy of Sciences; Morgan Churchill, of the University of Wisconsin Oshkosh; Evan Martin, of the San Diego Natural History Museum; and Sarah Boessenecker, of the University of Leicester, United Kingdom.

They found that genuine fossil occurrences were present until the end of the early Pliocene epoch, 3.6 million years ago. All later fossils either had poor data provenance and likely came from other fossil sites or showed evidence of being eroded from older deposits. Until 3.6 million years ago, O. megalodon had a continuous fossil record on the West Coast.

“We used the same worldwide dataset as earlier researchers but thoroughly vetted every fossil occurrence, and found that most of the dates had several problems-fossils with dates too young or imprecise, fossils that have been misidentified, or old dates that have since been refined by improvements in geology; and we now know the specimens are much younger,” Boessenecker said.

“After making extensive adjustments to this worldwide sample and statistically re-analyzing the data, we found that the extinction of O. megalodon must have happened at least one million years earlier than previously determined.”

This is a substantial adjustment as it means that O. megalodon likely went extinct long before a suite of strange seals, walruses, sea cows, porpoises, dolphins and whales all disappeared sometime about 1-2.5 million years ago.

“The extinction of O. megalodon was previously thought to be related to this marine mass extinction-but in reality, we now know the two are not immediately related,” Boessenecker said.

It also is further unclear if this proposed mass extinction is actually an extinction, as marine mammal fossils between 1 and 2 million years old are extraordinarily rare-giving a two-million- year-long period of “wiggle room.”

“Rather, it is possible that there was a period of faunal turnover (many species becoming extinct and many new species appearing) rather than a true immediate and catastrophic extinction caused by an astronomical cataclysm like a supernova,” Boessenecker said.

The researchers speculate that competition with the newly evolved modern great white shark (Carcharodon carcharias) is a more likely reason for megalodon’s extinction.

Great whites first show up with serrated teeth about 6 million years ago and only in the Pacific; by 4 million years ago, they are finally found worldwide.

“We propose that this short overlap (3.6-4 million years ago) was sufficient time for great white sharks to spread worldwide and outcompete O. megalodon throughout its range, driving it to extinction-rather than radiation from outer space,” Boessenecker said.

A new study has documented unexpected consequences following the decline of great white sharks from an area off South Africa. The study found that the disappearance of great whites has led to the emergence of sevengill sharks, a top predator from a different habitat. A living fossil, sevengill sharks closely resemble relatives from the Jurassic period, unique for having seven gills instead of the typical five in most other sharks: here.

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Prehistoric hyenas, video


This 17 January 2019 video says about itself:

Chasmaporthetes, also known as hunting or running hyena, is an extinct genus of hyenas distributed in Eurasia, North America, and Africa. It lived during the Pliocene-Pleistocene epochs, from 4.9 million to 780,000 years ago, existing for about 4.12 million years.

The genus probably arose from Eurasian Miocene hyenas such as Thalassictis or Lycyaena, with C. borissiaki being the oldest known representative. It was a fast runner and an important carnivore on 4 continents during the Pliocene.

At least nine species are currently recognised. The genus type species is Chasmaporthetes ossifragus. It was assigned to Hyaenidae by Hay (1921), Geraads (1997), and Flynn (1998).

The species C. ossifragus was the only hyena to cross the Bering land bridge into the Americas. C. ossifragus ranged over what is now Arizona and Mexico during Blancan and early Irvingtonian Land Mammal ages, between 5.0 and 1.5 million years ago.

Chasmaporthetes was one of the so-called “dog-like” hyenas (of which the aardwolf is the only survivor), a hyaenid group which, in contrast to the now more common “bone-crushing” hyenas, evolved into slender-limbed, cursorial hunters like modern canids.

The genus has entered the popular culture lexicon as a result of cryptozoologic claims, having been proposed as the likely origin of the American Shunka Warakin and the Cuitlamiztli.

Chasmaporthetes was named by Hay (1921), who noted the name to be a reference to the possibility that the beginning of the Grand Canyon was witnessed by the North American species, C. ossifragus.

The limb bones of Chasmaporthetes were long and slender like those of cheetahs, and its cheek teeth were slender and sharp-edged like those of a cat. Chasmaporthetes likely inhabited open ground and was a daytime hunter.

In Europe, the species C. lunensis competed with the giant cheetah Acinonyx pardinensis, and may have preyed on the small bourbon gazelle (Gazella borbonica) and the chamois antelope (Procamptoceras brivatense).

The North American C. ossifragus was similar in build to C. lunensis, but had slightly more robust jaws and teeth. It may have preyed on the giant marmot Paenemarmota, and competed with the far more numerous Borophagus diversidens.

A study on the genus’ premolar intercuspid notches indicated Chasmaporthetes was likely hypercarnivorous rather than durophagous as its modern cousins (excluding the aardwolf) are.

Like most of the animals of the time, reasons for its extinction are not known.

‘Apeman’ toddler foot discovery


This 2015 video is called The Evolution From Ape To Man – Full Documentary.

From Dartmouth College in the USA:

Our human ancestors walked on two feet but their children still had a backup plan

Most complete foot of ancient human child ever

July 4, 2018

More than 3 million years ago, our ancient human ancestors, including their toddler-aged children, were standing on two feet and walking upright, according to a new study published in Science Advances.

“For the first time, we have an amazing window into what walking was like for a 2½-year-old, more than 3 million years ago”, says lead author, Jeremy DeSilva, an associate professor of anthropology at Dartmouth College, who is one of the world’s foremost authorities on the feet of our earliest ancestors. “This is the most complete foot of an ancient juvenile ever discovered.”

The tiny foot, about the size of a human thumb, is part of a nearly complete 3.32-million-year-old skeleton of a young female Australopithecus afarensis discovered in 2002 in the Dikika region of Ethiopia by Zeresenay (Zeray) Alemseged, a professor of organismal biology and anatomy at the University of Chicago and senior author of the study. Alemseged is internationally known as a leading paleontologist on the study of human origins and human evolution.

“Placed at a critical time and the cusp of being human, Australopithecus afarensis was more derived than Ardipithecus (a facultative biped) but not yet an obligate strider like Homo erectus. The Dikika foot adds to the wealth of knowledge on the mosaic nature of hominin skeletal evolution” explained Alemseged.

Given that the fossil of the tiny foot is the same species as the famous Lucy fossil and was found in the same vicinity, it is not surprising that the Dikika child was erroneously labeled “Lucy’s baby” by the popular press, though this youngster lived more than 200,000 years before Lucy.

In studying the fossil foot’s remarkably preserved anatomy, the research team strived to reconstruct what life would have been like years ago for this toddler and how our ancestors survived. They examined what the foot would have been used for, how it developed and what it tells us about human evolution. The fossil record indicates that these ancient ancestors were quite good at walking on two legs. “Walking on two legs is a hallmark of being human. But, walking poorly in a landscape full of predators is a recipe for extinction”, explained DeSilva.

At 2½ years old, the Dikika child was already walking on two legs, but there are hints in the fossil foot that she was still spending time in the trees, hanging on to her mother as she foraged for food. Based on the skeletal structure of the child’s foot, specifically, the base of the big toe, the kids probably spent more time in the trees than adults. “If you were living in Africa 3 million years ago without fire, without structures, and without any means of defense, you’d better be able get up in a tree when the sun goes down”, added DeSilva. “These findings are critical for understanding the dietary and ecological adaptation of these species and are consistent with our previous research on other parts of the skeleton especially, the shoulder blade”, Alemseged noted.

See also here.

Ancient tools and bones discovered in China by archaeologists suggest early humans left Africa and arrived in Asia earlier than previously thought: here.

Ancient fossil bear discovery in Canada


This video says about itself:

18 December 2017

Paddington‘s prehistoric ancestor, a primitive bear with a sweet tooth, has been discovered in the Arctic. Researchers identified the remains of a 3.5-million-year-old bear from a fossil-rich site in Canada’s High Arctic. The findings show that the animal is a close relative of the ancestor of modern bears, and that it also had a taste for sweet treats – shown by cavities in its teeth. They say the ancient bear may have got his bad teeth from munching on berries, rather than Paddington’s preferred sweet treat of marmalade sandwiches.

From the Natural History Museum of Los Angeles County in the USA:

Primitive fossil bear with a sweet tooth identified from Canada’s High Arctic

December 18, 2017

Researchers from the Canadian Museum of Nature and the Natural History Museum of Los Angeles County have identified remains of a 3.5-million-year-old bear from a fossil-rich site in Canada’s High Arctic. Their study shows not only that the animal is a close relative of the ancestor of modern bears — tracing its ancestry to extinct bears of similar age from East Asia — but that it also had a sweet tooth, as determined by cavities in the teeth.

The scientists identify the bear as Protarctos abstrusus, which was previously only known from a tooth found in Idaho. Showing its transitional nature, the animal was slightly smaller than a modern black bear, with a flatter head and a combination of primitive and advanced dental characters. The results are published today in the journal Scientific Reports.

“This is evidence of the most northerly record for primitive bears, and provides an idea of what the ancestor of modern bears may have looked like,” says Dr. Xiaoming Wang, lead author of the study and Head of Vertebrate Paleontology at the Natural History Museum of Los Angeles County (NHMLA). “Just as interesting is the presence of dental caries, showing that oral infections have a long evolutionary history in the animals, which can tell us about their sugary diet, presumably from berries. This is the first and earliest documented occurrence of high-calorie diet in basal bears, likely related to fat storage in preparation for the harsh Arctic winters.”

The research team, which included co-author Dr. Natalia Rybczynski, a Research Associate and paleontologist with the Canadian Museum of Nature, were able to study recovered bones from the skull, jaws and teeth, as well as parts of the skeleton from two individuals.

The bones were discovered over a 20-year period by Canadian Museum of Nature scientists, including Dr. Rybczynski, at a fossil locality on Ellesmere Island known as the Beaver Pond site. The peat deposits include fossilized plants indicative of a boreal-type wetland forest, and have yielded other fossils, including fish, beaver, small carnivores, deerlets, and a three-toed horse.

The findings show that the Ellesmere Protarctos lived in a northern boreal-type forest habitat, where there would have been 24-hour darkness in winter, as well as about six months of ice and snow.

“It is a significant find, in part because all other ancient fossil ursine bears, and even some modern bear species like the sloth bear and sun bear, are associated with lower-latitude, milder habitats,” says co-author Dr. Rybczynski. “So, the Ellesmere bear is important because it suggests that the capacity to exploit the harshest, most northern forests on the planet is not an innovation of modern grizzlies and black bears, but may have characterized the ursine lineage from its beginning.”

Dr. Wang analyzed characteristics of fossil bear remains from around the world to identify the Ellesmere remains as Protarctos and to establish its evolutionary lineage in relation to other bears. Modern bears are wide-ranging, found from equatorial to polar regions. Their ancestors, mainly found in Eurasia, date to about 5 million years ago.

Fossil records of ursine bears (all living bears plus their ancestors, except the giant panda, which is an early offshoot) are poor and their early evolution controversial. The new fossil represents one of the early immigrations from Asia to North America but it is probably not a direct ancestor to the modern American black bear.

Of further significance is that the teeth of both Protarctos individuals show signs of well-developed dental cavities, which were identified following CT scans by Stuart White, a retired professor with the UCLA School of Dentistry. The cavities underline that these ancient bears consumed large amounts of sugary foods such as berries. Indeed, berry plants are found preserved in the same Ellesmere deposits as the bear remains.

“We know that modern bears consume sugary fruits in the fall to promote fat accumulation that allows for winter survival via hibernation. The dental cavities in Protarctos suggest that consumption of sugar-rich foods like berries, in preparation for winter hibernation, developed early in the evolution of bears as a survival strategy,” explains Rybczynski.

South Africa’s oldest Australopithecus fossil


This video from South Africa says about itself:

6 December 2017

The Australopithecus fossil, Little Foot, was discovered by Wits [University of the Witwatersrand] palaeoanthropologist Ron Clarke.

From the University of the Witwatersrand in South Africa:

Litte Foot takes a bow

South Africa’s oldest, and the world’s most complete Australopithecus skeleton ever found, introduced to the world

December 6, 2017

South Africa’s status as a major cradle in the African nursery of humankind has been reinforced with today’s unveiling of “Little Foot”, the country’s oldest, virtually complete fossil human ancestor.

Little Foot is the only known virtually complete Australopithecus fossil discovered to date. It is by far the most complete skeleton of a human ancestor older than 1.5 million years ever found. It is also the oldest fossil hominid in southern Africa, dating back 3.67 million years. The unveiling will be the first time that the completely cleaned and reconstructed skeleton can be viewed by the national and international media.

Discovered by Professor Ron Clarke from the Evolutionary Studies Institute at the University of the Witwatersrand in Johannesburg, South Africa, the fossil was given the nickname of “Little Foot” by Prof. Phillip Tobias, based on Clarke’s initial discovery of four small footbones. Its discovery is expected to add a wealth of knowledge about the appearance, full skeletal anatomy, limb lengths and locomotor abilities of one of the species of our early ancestral relatives.

“This is one of the most remarkable fossil discoveries made in the history of human origins research and it is a privilege to unveil a finding of this importance today,” says Clarke.

After lying undiscovered for more than 3.6 million years deep within the Sterkfontein caves about 40km north-west of Johannesburg, Clarke found several foot bones and lower leg bone fragments in 1994 and 1997 among other fossils that had been removed from rock blasted from the cave years earlier by lime miners. Clarke sent his assistants Stephen Motsumi and Nkwane Molefe into the deep underground cave to search for any possible broken bone surface that might fit with the bones he had discovered in boxes. Within two days of searching, they found such a contact, in July 1997.

Clarke realised soon after the discovery that they were on to something highly significant and started the specialised process of excavating the skeleton in the cave up through 2012, when the last visible elements were removed to the surface in blocks of breccia. “My assistants and I have worked on painstakingly cleaning the bones from breccia blocks and reconstructing the full skeleton until the present day,” says Clarke.

In the 20 years since the discovery, they have been hard at work to excavate and prepare the fossil. Now Clarke and a team of international experts are conducting a full set of scientific studies on it. The results of these studies are expected to be published in a series of scientific papers in high impact, peer reviewed international journals in the near future.

This is the first time that a virtually complete skeleton of a pre-human ancestor from a South African cave has been excavated in the place where it was fossilised.

“Many of the bones of the skeleton are fragile, yet they were all deeply embedded in a concrete-like rock called breccia,” Clarke explains.

“The process required extremely careful excavation in the dark environment of the cave. Once the upward-facing surfaces of the skeleton’s bones were exposed, the breccia in which their undersides were still embedded had to be carefully undercut and removed in blocks for further cleaning in the lab at Sterkfontein,” says Clarke.

The 20-year long period of excavation, cleaning, reconstruction, casting, and analysis of the skeleton has required a steady source of funding, which was provide by the Palaeontological Scientific Trust (PAST) — a Johannesburg-based NGO that promotes research, education and outreach in the sciences related to our origins. Among its many initiatives aimed at uplifting the origin sciences across Africa, PAST has been a major funder of research at Sterkfontein for over two decades.

Professor Adam Habib, Vice-Chancellor and Principal of the University of the Witwatersrand says: “This is a landmark achievement for the global scientific community and South Africa’s heritage. It is through important discoveries like Little Foot that we obtain a glimpse into our past which helps us to better understand our common humanity.”

PAST’s chief scientist Professor Robert Blumenschine labels the discovery a source of pride for all Africans. “Not only is Africa the storehouse of the ancient fossil heritage for people the world over, it was also the wellspring of everything that makes us human, including our technological prowess, our artistic ability, and our supreme intellect,” he says.

The scientific value of the find and much more will be unveiled in a series of papers that Prof Clarke and a team of international experts have been preparing, with many expected in the next year.

New research shows that the climate of the interior of southern Africa almost two million years ago was much wetter than the modern environment. This first extensive paleoenvironmental sequence for the interior of southern Africa suggests that human ancestors were living in environments other than open, arid grasslands known from East African research of the same time period: here.

“Our study revealed that the cranium of the Jacovec specimen and of the Australopithecus specimens from Sterkfontein in general was thick and essentially composed of spongy bone,” says Beaudet. “This large portion of spongy bone, also found in our own cranium, may indicate that blood flow in the brain of Australopithecus may have been comparable to us, and/or that the braincase had an important role in the protection of the evolving brain”: here.

A nearly complete hominid skeleton known as Little Foot has finally been largely freed from the stony shell in which it was discovered in a South African cave more than 20 years ago. And in the first formal analyses of the fossils, researchers say the 3.67-million-year-old Little Foot belonged to its own species. In four papers posted online at bioRxiv.org between November 29 and December 5, paleoanthropologist Ronald Clarke of the University of the Witwatersrand in Johannesburg and colleagues assign Little Foot to a previously proposed species, Australopithecus prometheus, that has failed to gain traction among many researchers: here.

Pliocene big marine life extinction discovered


This video from the USA says about itself:

Pliocene Epoch – Florida Fossils: Evolution of Life and Land

2 February 2010

This video from the Museum’s Florida Fossils exhibit describes the Pliocene Epoch, 5 million to 2 million years ago The formation of a land bridge across Panama in Central America about 3 million years ago was a major biotic event. Both North and South America had been previously isolated for millions of years. Each had evolved its own unique flora and fauna.

Contact between North and South America allowed for the overland dispersal of organisms between the two continents. Mammals living in North America invaded South America, and South American mammals moved north. The closure of the seaway between North and South America apparently resulted in extinctions of many marine organisms. However, newly formed habitats also promoted the evolution of many new species.

Produced, directed and filmed for the Florida Museum of Natural History by Wes C. Skiles/Karst Productions, Inc.

From the University of Zurich in Switzerland:

Previously unknown extinction of marine megafauna discovered

June 26, 2017

Summary: Over two million years ago, a third of the largest marine animals like sharks, whales, sea birds and sea turtles disappeared. This previously unknown extinction event not only had a considerable impact on the earth’s historical biodiversity but also on the functioning of ecosystems.

The disappearance of a large part of the terrestrial megafauna such as saber-toothed cat and the mammoth during the ice age is well known. Now, researchers at the University of Zurich and the Naturkunde Museum in Berlin have shown that a similar extinction event had taken place earlier, in the oceans.

New extinction event discovered

The international team investigated fossils of marine megafauna from the Pliocene and the Pleistocene epochs (5.3 million to around 9,700 years BC). “We were able to show that around a third of marine megafauna disappeared about three to two million years ago. Therefore, the marine megafaunal communities that humans inherited were already altered and functioning at a diminished diversity,” explains lead author Dr. Catalina Pimiento, who conducted the study at the Paleontological Institute and Museum of the University of Zurich.

Above all, the newly discovered extinction event affected marine mammals, which lost 55 per cent of their diversity. As many as 43 per cent of sea turtle species were lost, along with 35 per cent of sea birds and 9 per cent of sharks. On the other hand, the following new forms of life were to develop during the subsequent Pleistocene epoch: Around a quarter of animal species, including the polar bear Ursus [maritimus], the storm petrel Oceanodroma or the penguin Megadyptes had not existed during the Pliocene. Overall, however, earlier levels of diversity could not be reached again.

Effects on functional diversity

In order to determine the consequences of this extinction, the research team concentrated on shallow coastal shelf zones, investigating the effects that the loss of entire functional entities had on coastal ecosystems. Functional entities are groups of animals not necessarily related, but that share similar characteristics in terms of the function they play on ecosystems. The finding: Seven functional entities were lost in coastal waters during the Pliocene.

Even though the loss of seven functional entities, and one third of the species is relatively modest, this led to an important erosion of functional diversity: 17 per cent of the total diversity of ecological functions in the ecosystem disappeared and 21 per cent changed. Previously common predators vanished, while new competitors emerged and marine animals were forced to adjust. In addition, the researchers found that at the time of the extinction, coastal habitats were significantly reduced due to violent sea levels fluctuations.

Large warm-blooded marine animals are more vulnerable to global environmental changes

The researchers propose that the sudden loss of the productive coastal habitats, together with oceanographic factors such as altered sea currents, greatly contributed to these extinctions. “Our models have demonstrated that warm-blooded animals in particular were more likely to become extinct. For example, species of sea cows and baleen whales, as well as the giant shark Carcharocles megalodon disappeared,” explains Dr. Pimiento. “This study shows that marine megafauna were far more vulnerable to global environmental changes in the recent geological past than had previously been assumed.” The researcher also points to a present-day parallel: Nowadays, large marine species such as whales or seals are also highly vulnerable to human influences.

Australopithecus footprints, new discovery in Tanzania


This video says about itself:

28 January 2016

This animated short film recounts the life and work of paleoanthropologist Mary Leakey, including her discovery of the Laetoli footprints.

Forty years ago in Laetoli, Tanzania, a team of paleontologists discovered a set of 3.6-million-year-old fossil footprints of early hominids —likely our ancestors. The team was led by Mary Leakey, the pioneering subject of this animated feature. The film covers many highlights of her career and her relationship with her research partner and husband, Louis Leakey. Leakey described the discovery of the Laetoli footprints as one of her most important finds.

From Science News:

New footprint finds suggest range of body sizes for Lucy’s species

Sign of tallest known Australopithecus afarensis individual unearthed in Tanzania

By Bruce Bower

1:04pm, December 16, 2016

Famous footprints of nearly 3.7-million-year-old hominids, found in 1976 at Tanzania’s Laetoli site, now have sizable new neighbors.

While excavating small pits in 2015 to evaluate the impact of a proposed field museum at Laetoli, researchers uncovered comparably ancient hominid footprints about 150 meters from the original discoveries. The new finds reveal a vast range of body sizes for ancient members of the human evolutionary family, reports an international team led by archaeologists Fidelis Masao and Elgidius Ichumbaki, both of the University of Dar es Salaam in Tanzania.

A description of the new Laetoli footprints appears online December 14 in eLife.

Scientists exposed 14 hominid footprints, made by two individuals as they walked across wet volcanic ash. More than 500 footprints of ancient horses, rhinos, birds and other animals dotted the area around the hominid tracks. Like previously unearthed tracks of three individuals who apparently strode across the same layer of soft ash at the same time, the latest footprints were probably made by members of Australopithecus afarensis, the team says. Best known for Lucy, a partial skeleton discovered in Ethiopia in 1974, A. afarensis inhabited East Africa from around 4 million to 3 million years ago.

All but one of the 14 hominid impressions come from the same individual. Based on footprint dimensions, the researchers estimate that this presumed adult male — nicknamed Chewie in honor of the outsized Star Wars character Chewbacca — stood about 5 feet 5 inches tall and weighed nearly 100 pounds. That makes him the tallest known A. afarensis. The team calculates that the remaining hominid footprint was probably made by a 4-foot-9-inch female who weighed roughly 87 pounds. Stature estimates based on the other three Laetoli footprint tracks fall below that of the ancient female.

Lucy lived later than the Laetoli crowd, around 3.2 million years ago, and was about 3 ½ feet tall.

If Laetoli’s five impression-makers were traveling together, “we can suppose that the Laetoli social group was similar to that of modern gorillas, with one large male and a harem of smaller females and perhaps juveniles,” says paleontologist and study coauthor Marco Cherin of the University of Perugia in Italy.

Chewie’s stature challenges a popular assumption that hominid body sizes abruptly increased with the emergence of the Homo genus, probably shortly after A. afarensis died out, Cherin adds.

The new paper presents reasonable stature estimates based on the Laetoli footprints, but “we don’t have a firm idea of how foot size was related to overall body size in Australopithecus,” says evolutionary biologist Kevin Hatala of Chatham University in Pittsburgh. Masao’s group referred to size data from present-day humans to calculate heights and weights of A. afarensis footprint-makers. That approach “could lead to some error,” Hatala says.

Stature estimates based on footprints face other obstacles, says paleoanthropologist Yohannes Haile-Selassie of the Cleveland Museum of Natural History. For instance, some tall individuals have small feet and short folks occasionally have long feet. It’s also unclear whether the new footprints and those from 1976 represent a single group, or if some smaller footprints were also made by males, Haile-Selassie adds. Cherin’s proposal that large A. afarensis males controlled female harems “is a bit of a stretch,” Haile-Selassie says.

The new report doesn’t document surprisingly large size differences among members of Lucy’s kind, Haile-Selassie adds. A. afarensis fossils previously excavated in Ethiopia include a partial male skeleton now estimated by Haile-Selassie and his colleagues to have been only about three inches shorter than Chewie’s reported height (SN: 7/17/10, p. 5).