May 15, 2019

Last month, on April 10, scientists announced that fossils discovered in the Philippines were evidence of a new and previously unknown variety of human that inhabited the islands some 67,000 years ago. The fossils were found at Callao Cave in northern Luzon, the main island of the Philippines. The scientists determined that the fossils represent a new species of human beings called Homo luzonensis.

Scientists found the bones of Homo luzonensis at Callao Cave on the Philippine island of Luzon. Credit: Callao Cave Archaeology Project

The fossil remains of Homo luzonensis were discovered during excavations that took place at Callao Cave from 2007 through 2015. The remains of three individuals included isolated teeth, a foot bone, two toe bones, two finger bones, and an incomplete thigh bone. Scientists observed an odd mix of anatomical features in these few remains. Some of the features are seen in modern humans alive today. Other features, such as highly curved toe bones, are seen in primitive human ancestors called Australopithecines.

These teeth of Homo luzonensis were found in Callao Cave. Credit: © Callao Cave Archaeology Project

The fossils from Luzon add to the growing list of physically distinct varieties of prehistoric humans known across the world—a list that has complicated the view of human evolution. Scientists understand from fossil evidence that physically modern human beings, Homo sapiens, first appeared in the fossil record of Africa around 200,000 years ago. Scientists believe those people eventually spread to inhabit nearly every corner of the globe. However, many regions of Africa, Asia, and Europe were already occupied by prehistoric humans when Homo sapiens arrived.

This foot bone of Homo luzonensis shows unusual curvature. Credit: © Callao Cave Archaeology Project

The Neandertals, a well known group of prehistoric humans, inhabited much of Europe and Central Asia at least 250,000 years ago. Another group, known informally as the Denisovans, is identified by genetic material recovered from a few bones discovered in Siberia (and recently, Tibet) that date to more than 50,000 years ago. Scientist do not know what the Denisovans looked like because fossil remains are so scarce, but their DNA shows they were distinct from both Neandertals and modern humans. These early people are also different from Homo naledi, a mysterious early human species first discovered at Rising Star Cave in South Africa in 2015. Even more peculiar is Homo floresiensis, a diminutive (very small) variety of prehistoric humans known from fossils discovered on the Indonesian island of Flores in 2004.

Scientist now understand that early Homo sapiens shared their world with several other physically distinct varieties of human beings. These ancient people were more like cousins than ancestors to modern humans. Today, only physically modern people remain. The discovery of yet another previously unknown human species demonstrates that prehistoric people came in many shapes and sizes.

November 24, 2017

Today, November 24, is Evolution Day, a celebration of the day British naturalist Charles Darwin published On the Origin of Species on Nov. 24, 1859. The groundbreaking book presented Darwin’s theory of evolution. Since then, advances in various scientific fields have resulted in refinements of the theory. The main ideas of evolution, however, have remained largely unchanged.

Charles Darwin, a British naturalist, became famous for his theories on evolution. Credit: © Time Life Pictures, Getty Images

Darwin’s theory of evolution included several related ideas. These ideas included the belief that evolution had occurred and that most evolutionary change was gradual, requiring thousands or millions of years. Darwin also proposed that the primary mechanism for evolution was a process called natural selection. He said that the millions of species on Earth arose from a single original life form through a branching process called speciation. By speciation, one species can give rise to two or more species. The full title of Darwin’s book is On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life.

Darwin’s theories shocked most people of his day. They believed that each species had been created by a separate divine act. Darwin’s book, which is usually called simply The Origin of Species, presented facts that refuted this belief. It caused a revolution in biological science and greatly affected religious thought. Since the book’s publication, religious groups have tried to discredit the theory of evolution because it conflicts with their religious beliefs. For example, they claim that the theory of evolution disagrees with the Biblical account of the Creation. Some people argue against the theory of natural selection because they believe it diminishes the role of divine guidance in the universe. Scientists—and science itself—fully embrace evolution, however, and use millions of examples as proof.

April 19, 2017

A recent study has found a connection between hereditary sickle cell disease and malaria, a dangerous parasitic disease transmitted by mosquitoes. The study determined that genetic mutation responsible for sickle cell disease, a serious blood disorder, rapidly spread through human populations in Africa more than 40,000 years ago mainly because it provides protection from malaria. Genetic scientists used computer-based models to understand the conditions that spread the sickle cell mutation among certain human populations. The scientists learned that this mutation was among the most important factors affecting survival over the last 40,000 years for people living in malaria-affected regions. The study’s results were published on March 10, 2017, in the scientific journal PLOS Genetics.

A new study has shown that people carrying the sickling gene that can cause sickle cell disease have a higher natural resistance to malaria parasites, shown here in pink and blue. Credit: © CNRI/SPL from Photo Researchers

Sickle cell disease, also called sickle cell anemia, is a hereditary blood disease. In the United States, it occurs chiefly among African Americans. It also affects other groups, including people of Central African, Mediterranean, Middle Eastern, and South Asian origin. Sickle cell patients have an abnormal type of hemoglobin, the oxygen-carrying protein that gives red blood cells their color. This abnormal protein, called sickle hemoglobin, or hemoglobin S, forms crystals in red blood cells. This causes the normally round red blood cells to change into twisted, rigid sickle-shaped forms. The sickle cells can get trapped and block the normal flow of blood through blood vessels. This disruption of blood flow causes periodic crises (attacks of severe pain and fever) and related problems including strokes, lung or kidney damage, and sudden death.

This magnified blood sample shows the red blood cells of a person with sickle cell anemia. Normal red blood cells appear round in the image. But, abnormal, sickle hemoglobin causes many red blood cells to change into twisted, rigid sickle forms. Credit: © Bruce Coleman Inc./Alamy Images

Scientists know that harmful mutations, such as the one responsible for the abnormal sickle hemoglobin, should become less common in populations over time because of the process of natural selection. Natural selection sorts out these random changes according to their value in enhancing the individual’s reproduction and survival. In the past, people with sickle cell disease rarely survived long enough to have children. Today, modern medicine has improved the health and life span of people with the condition.

Scientists have lately learned that carriers of the sickling gene—that is, people who have only one copy of the mutated gene instead of two—not only have normal blood cells, but they also have a higher natural resistance than noncarriers to malaria. Sickle cell anemia is a rare disorder, but it occurs most often among populations that live in areas threatened by malaria. Thus, the sickling gene—despite its negative effects for some—represented an important advantage for other people in these tropical and subtropical regions. The new research shows that the sickle cell mutation had a rapid and dramatic effect in shaping the genetic makeup of certain human populations in the past. Such dramatic changes are also possible in the future, as human populations continue to adapt to a constantly changing global environment.

November 23, 2016

At a recent convention of paleontologists (scientists who study animals and plants that lived in prehistoric times), things got a bit venomous. A group of researchers claimed that a fossil recently identified as an early snake was not a snake at all. Furthermore, they stated that the specimen should not have been studied in the first place. The presentation was the most recent shot fired in the battle over the evolution (a process of change over time) of snakes.

This artist’s impression shows the four-footed tetrapodophis amplectus snatching its prey, an unlucky salamander. Credit: © James Brown, University of Portsmouth

In 2015, Dave Martill and his colleagues at the University of Portsmouth in England reported that they had discovered a new type of primitive snake. They found the ancient animal’s fossilized imprint (which came from Brazil) among the collections of a German museum. The British researchers named their discovery Tetrapodophis amplectus and published their findings in the journal Science. Tetrapodophis means “four-footed snake.” The animal was about 6 inches (15 centimeters) long and possessed four tiny limbs. It lived in an ocean environment some 110 million years ago.

This month, however, at the annual Society of Vertebrate Paleontology conference in Salt Lake City, Utah, Michael Caldwell of the University of Alberta in Edmonton, Canada, gave a presentation refuting Martill’s “four-footed snake” diagnosis. In the creature’s skull, for instance, Caldwell noted “every single character that was identified in the original manuscript as being diagnostic of a snake was either not the case or not observable.” Instead, Caldwell’s group contended that Tetrapodophis is not a snake at all, but rather a member of a group of unrelated marine reptiles.

The fossilized imprint of Tetrapodophis reveals small, specialized feet—or perhaps flippers. Credit: © Dave Martill, University of Portsmouth

This dispute is merely the latest spat among paleontologists on snake origins. Paleontologists agree that snakes likely evolved in the Jurassic Period some 150 million years ago. Some people (like Martill) think that snakes evolved from aquatic reptiles. Over million of years, four-legged reptiles would have spent more and more time in the water, eventually losing their limbs in favor of a long body good for swimming. Later, snakes made their way onto land, with some (sea snakes) remaining in their ancestral habitat. Martill’s group contends that snakes were closely related to mosasaurs, giant marine reptiles that prowled the oceans some 100 million years ago. Most paleontologists, however, think that snakes evolved from burrowing, terrestrial reptiles. As these aimals dug deeper and more complex burrows with their strong heads, their limbs vanished over millions of years. Later, snakes moved into different habitats, including the sea. In this scenario, snakes’ closest relatives would be monitor lizards such as the Komodo dragon. So far, a lack of ancient snake fossils has prevented either hypothesis from being proven.

Further muddying the water, Caldwell—of the “land snake” faction—reported that when he went to study the fossil in the German museum, the fossil was no longer there. Apparently, it had been a loan to the museum from a private collector. The collector had retrieved it from the museum because it had been damaged during an earlier study. Most paleontologists will not study privately owned fossils for this exact reason: an owner may take back the fossil at any time. Science must be repeatable, so a description of a specimen that is no longer available for study is not science at all. Since Tetrapodophis was revealed to be a privately owned specimen, many experts have vowed to ignore it while conducting future studies on snake evolution. We will have to wait for more fossils—in the permanent collections of museums and universities—to determine if snakes started out on land or in the water—with four legs or, perhaps, four flippers.

September 12, 2016

Bigfoot and Yowie (a large, hairy ape said to live in the wild regions of Australia) might be mere legends, but one giant ape was certainly more than myth. Standing at a whopping 10 feet (3 meters) tall and weighing more than 900 pounds (400 kilograms), Gigantopithecus was about twice the size of a large male gorilla, making it the largest ape that ever lived. Gigantopithecus walked on its hands and fists, like today’s great apes, and roamed the tropical forests of what are now southern China, northern Vietnam, and northern India. Scientists believe that Gigantopithecus was related to ancestors of the modern orangutan.

A Gigantopithecus replica (known as “Mr. G”) was installed at the Museum of Man in San Diego, California, in 2003. Credit: © ZUMA Press/Alamy Images

Gigantopithecus’s fellow jungle creatures had only to worry about being squashed, because the colossal ape was not a meat-eater. Instead, it ate such hardy foods as bamboo and durian (a tropical fruit with a hard, prickly outer skin), using its large jaws and teeth to chew the tough plant matter. It is quite possible that crocodiles and ancient relatives of tigers and hyenas fed on Gigantopithecus young, but adults were so enormous that predators probably left them alone.

Gigantopithecus lived from more than 8 million years ago to about 200,000 years ago. It may have disappeared as the result of a shift in southern Asia’s climate about 1 million years ago, when conditions became colder and drier and the giant ape’s forest home began to shrink. Scientists believe that Homo erectus, an ancient relative of humans, crossed paths with Gigantopithecus and may have hunted it, playing a role in the monstrous beast’s extinction.

August 24, 2016

Monkeys in the Amazon rain forest likely entered their own Stone Age more than 700 years ago, according to scientists investigating a fascinating site at Serra da Capivara National Park in northeastern Brazil. At the site, scientists from the University of Oxford in the United Kingdom and from Brazil’s University of São Paulo observed bearded capuchin monkeys (Sapajus libidinosus) using rocks as hammers to crush hard-shelled nuts atop flat stone anvils. The scientists discovered dozens of discarded stone hammers and anvils once they began shallow excavations at a site regularly visited by the monkeys. The scientists determined that monkeys have been using simple stone tools at that site for more than 700 years. The findings were described in the July 2016 issue of the journal Current Biology.

A capuchin monkey uses stones to crack a cashew nut in Serra da Capivara National Park in northeast Brazil. Credit: © Michael Haslam, Primate Archaeology Project/University of Oxford

Stone Age is a term used to designate the period when prehistoric people used stone, rather than metal, tools. For humans, the Stone Age began about 3.3 million years ago, when small stones were first made into crude chopping tools by prehuman ancestors called Australopithecines. It ended in the Near East about 3000 B.C., when bronze replaced stone as the chief material from which tools were made.

In dry northeastern Brazil, hard-shelled fruits and seeds are more common than the fruit and succulent leaves that capuchins prefer. Centuries ago, a clever capuchin figured out how to pound open a nut using a heavy stone as a hammer on a heavier flat stone anvil, thereby opening up an entirely new and abundant source of food. The scientists observed that the monkeys will carefully select hammer stones and bring them to trees bearing nuts and fruits. The monkeys then stash the stones in hidden spots around the trees for later use. The research site in Brazil is littered with such stones that have accumulated over centuries.

For many years, scientists considered humans to be the only species that made extensive use of tools. In the 1960’s, however, naturalist Jane Goodall discovered that wild chimpanzees in Africa make and use simple tools. Goodall observed them stripping tree twigs and using the twigs as tools for catching termites. She also observed chimpanzees using rocks to break open hard-shelled palm nuts in the forest.

Earlier in 2016, some of the scientists involved in the Brazil research published observations of monkeys called macaques using stones to break open shellfish and nuts in Thailand. Now, with the Brazilian study, there seems little doubt that some species of nonhuman primates have long since entered their own Stone Age. The site in Brazil provides scientists with a unique opportunity to study the ecological, social, and cognitive (mental) factors that likely played a role in the development of technology and culture millions of years ago at the dawn of humankind.

March 23, 2016

A recreation of a horse-sized tyrannosaur, Timurlengia euotica, stalks through its natural environment of 90 million years ago. Two other reptiles (Azhdarcho longicollis) fly nearby. The newly-discovered fossilized remains of a Timurlengia euotica reveal how Tyrannosaurus rex and its close relatives became top predators. Credit: © Todd Marshall (Smithsonian)

Rex means king, and, sure enough, Tyrannosaurus rex was the king. As top predator at the end of the age of dinosaurs, T. rex hunted down prey with its heightened senses and tore them apart with its powerful jaws. It wasn’t always like that, however. Tens of millions of years earlier, the smaller ancestors of T. rex cowered from other predators called allosaurs (like the well-known Allosaurus). Little is known about how ancestors of T. rex evolved (changed over time) from small, nimble hunters into the huge predators of the Late Cretaceous (80-66 million years ago). Last week, a team of paleontologists, led by Stephen Brusatte of Scotland’s University of Edinburgh, announced a discovery, Timurlengia euotica, that helps fill in this gap in the Tyrant Lizard King’s family tree. The paleontologists announced their findings in the journal Proceedings of the National Academy of Sciences. 

Tyrannosaurus rex was a large, meat-eating dinosaur that lived about 68 to 65 million years ago in what is now western North America. It was one of the largest meat-eating dinosaurs, measuring about 40 feet (12 meters) long and about 12 feet (3.7 meters) high at the hip, and weighing about 7 short tons (6.3 metric tons). Similar animals roamed Asia and Europe. These monsters were the last of a group of meat-eating dinosaurs called tyrannosaurs, which came into existence some 150 million years ago.

Unlike the giant T. rex, most early tyrannosaurs were modestly sized hunters. They probably had hairlike feathers for warmth, camouflage, and display. Timurlengia reveals tyrannosaurs’ humble origins, but it also hints at their future dominance. It was a horse-sized tyrannosaur that lived in what is now Uzbekistan some 90 million years ago. The dinosaur is named for Timur (sometimes called Tamerlane, as in a poem by Edgar Allan Poe), a conqueror who ruled that region with an iron fist from the late 1300’s through the early 1400’s. Its specific name, euotica, references its keen sense of hearing. While Brusatte’s team only found a little over a dozen fragments of Timurlengia’s skeleton, some of these pieces contained a large inner ear, similar to later giant tyrannosaurs like T. rex. The fragments revealed that the dinosaur had a relatively large brain, also like its later cousins. Apparently, tyrannosaurs had all the smarts and sensory equipment to become top predators 90 million years ago, but they still lived in the shadow of the more primitive allosaurs.

At some point 80 to 90 million years ago, the allosaurs were replaced as apex predators by the tyrannosaurs, which eventually reached the giant proportions of T. rex. Although Stephen Brusatte and the team’s findings reveal that tyrannosaurs were already smart hunters with keen senses, it still isn’t known why exactly this change in dominant dinosaur occurred. Tyrannosaurs could have slowly replaced allosaurs because of their superior intelligence and senses. Or, an environmental disaster could have caused the allosaurs to go extinct, making room for the tyrannosaurs to thrive. More finds like Timurlengia will help scientists determine how tyrannosaurs emerged from the shadows to become the kings of the dinosaurs.

February 13, 2014

The discovery of a site in Canada containing hundreds of ancient fossils is being heralded as one of the most important discoveries in paleontology in the past 100 years. The huge fossil site, located in Marble Canyon in Kootenay National Park in southeastern British Columbia, contains hundreds of magnificently preserved fossils of early animals from the Cambrian, a period in Earth’s history that lasted from about 543 million to 490 million years ago. So far, scientists have found the fossils of more than 50 invertebrate (animals without backbones) species, about a dozen of which have never been seen before. The site rivals the famous Burgess Shale formation, a 505 million-year-old site discovered in 1909 in Yoho National Park about 26 miles (42 kilometers) northwest of Marble Canyon. For now, the exact location of the fossil deposit is being kept secret to protect the delicate fossils from collectors. The Marble Canyon site was discovered in 2012 by scientists fromt the Royal Ontario Museum, the Universities of Toronto and Saskatchewan in Canada, Pomona College in California, and Uppsala University in Sweden.

During the Cambrian Period, the region lay at the bottom of a shallow ocean. Fine-grained mud that accumulated over time preserved in exquisite detail the soft-bodied invertebrates that lived and died in this ocean over millions of years, giving paleontologists an excellent view of their anatomy. Many of the animals can be identified as types of worms and arthropods (animals with jointed legs). Among them are trilobites, an extinct group of arthropods related to modern crabs and lobsters. Some of the fossil animals appear similar to invertebrates alive today, while other are unique and are new to science.

A mold preserved the three-dimensional form of a trilobite after its body decayed. ((c) Sinclair Stammers, Science Photo Library; Photo Researchers)

The Cambrian Period was an important time in the history of life on Earth. Many major types of animals first appear in fossils from the early Cambrian Period. Scientists often refer to this sudden, dramatic increase in the variety of animal fossils as the Cambrian Explosion. During the Cambrian Explosion, animals evolved (developed gradually) into many new forms and spread throughout Earth’s oceans. They also began interacting with one another and their environment in more complex ways. Animals began eating other animals, growing skeletons for protection, and burrowing into sea-floor sediments for food and shelter.

The fossils unearthed from the Marble Canyon site will help researchers better understand the conditions of the marine ecosystem that spurred the rapid diversification of animal forms during the Cambrian Period. For example, some of the invertebrate species found at Marble Canyon are also known from fossil sites in Asia about the same age. This indicates that some species had spread throughout the world, while others may have been limited to particular habitats.

Additional World Book articles:

• Earth (History of Earth)
• Prehistoric animal
• How the Ocean Came to Be (a Special Report)
• Paleontology (1991) (a Back in Time article)

October 21, 2013

A 1.8-million-year-old fossil skull will almost certainly force scientists to trim some branches from the evolutionary “family tree” that eventually led to modern humans, paleoanthropologist David Lordkipanidze of the Georgian National Museum in Tbilisi suggested last week. The fossil, known simply as Skull 5, is one of several nearly complete fossil skulls discovered by Lordkipanidze and his team since 1991 at Dmanisi, a fossil site at the eastern end of the Black Sea in the Caucasus Mountains, about 50 miles (85 kilometers) southwest of Tbilisi. The skulls are among the most ancient fossils of human beings found outside of Africa, the cradle of humanity.

The Dmanisi fossil skulls have large browridges and projecting faces that lack chins. Scientists calculate that the skulls held brains that were about half the size of modern human brains. The skulls resemble those of early human ancestors found at fossil sites of about the same age in East Africa. Many scientists divide these ancestors into three species–Homo habilis, Homo rudolfensis, and Homo erectus. Some scientists argue that even more species of early humans existed nearly 2 million years ago, suggesting the human fossil “family tree” was more like a bush with many side branches.

A 1.8-million-year-old human fossil skull from Dmanisi, Republic of Georgia, displays thick skull bones; a low, sloping forehead; and a flat face. The species also had a thick ridge of bone above the eyes, called a browridge. (Mauricio Anton © 2002 National Geographic Society)

Lordkipanidze noted that Skull 5 and four others excavated at Dmanisi almost certainly represent a single population that lived in the same location at the same time. The skulls thus provide an unprecedented opportunity to measure the differences within a group of ancient humans. He found that the skulls showed remarkable differences in such features as the length of the jaw or thickness of the browridges. But, he said, the differences were no greater than those between any five modern people. All people alive today are members of single species, Homo sapiens.

Other anthropologists pointed out that if the five skulls from Dmanisi had been discovered at different sites in Africa, their physical differences could have led scientists to assign the skulls to different human species. The long-established habit of defining new species based on physical variation means that Skull 5 may have been classified as an entirely new human species.

Lordkipanidze and his colleague now theorize that there was only a single human species in Africa 1.8 million years ago and that same species is also represented at Dmanisi. They do not suggest what species that may be, but they recognize it as a member of our own genus, Homo. They argue that one or more of the early Homo species from Africa may need to be pruned from the human family tree.

Additional World Book articles:

• Archaeology
• Prehistoric people
• Stone Age
• Anthropology (2002) (a Back in Time article)
• Anthropology (2007) (a Back in Time article)

Polar bears are more distantly related to other bears than previously thought, according to new research. Scientists have long known that polar bears share a common ancestor with brown bears. Previous research had shown that the split between the two groups occurred relatively recently, about 150,000 years ago. But in new research, scientists found that the split took place much earlier, about 600,000 years ago. Thus, polar bears are more distinct from other bears than scientists thought.

The research helps scientists to understand the history of how polar bears have evolved (developed over many generations). Polar bears have many adaptations (features) that help them to survive on Arctic sea ice. These adaptations help to make them different from brown bears. Polar bears would have had to evolve these adaptations in relatively little time if they had split from the same ancestor as brown bears only 150,000 years ago.

The new research involved studying bear DNA, which carries hereditary information. Scientists compared the DNA of black bears, brown bears, and polar bears. Comparing the DNA enabled scientists to estimate the date at which polar bears and brown bears shared a common ancestor. Earlier research into polar bear origins used DNA from a different part of the cell. Most DNA is housed in the cell’s nucleus (a body at the center of the cell). However, a small amount of DNA is housed in mitochondria (tiny bodies in the cell that burn chemical energy). The earlier research used DNA from the mitochondria to estimate the first appearance of polar bears. The new research used DNA from the nucleus. This information provided more data about polar bear origins.

The hardy polar bear lives along the frozen shores and in the icy waters of the Arctic Ocean. Polar bears have a thick, white coat that blends in with the ice and snow. They swim strongly by paddling with their front legs and stretching their head forward. (Marvin E. Newman, DPI)

Scientists suggest the different estimates for the first appearance of polar bears may have been caused by later matings between polar bears and brown bears. Such mating is known to occur, especially when polar bear populations are under stress. Thus, the mitochondria results may record breeding between polar bears and brown bears about 150,000 years ago. In fact, the research suggested that polar bears have gone through several so-called bottlenecks, periods during which relatively few polar bears survived. These bottlenecks may have corresponded to reduced sea ice or other climate changes that made it more difficult for polar bears to survive. Polar bears are currently considered vulnerable to extinction because of a loss of sea ice caused by climate change, and scientists have shown that some polar bears and brown bears have breed in recent years. The research was published online in the journal Science.

Additional World Book articles:

The Great Meltdown (a special report)