Category Zoology

Who were our first ancestors?

Humans belong to a group of mammals called primates. It includes apes, monkeys and several much smaller animals such as lemurs and bush babies. As much as 50 million years ago, back in the Eocene Period, there were traces of primate-like animals. They were small and looked rather like squirrels, but their eyes faced forwards like modern monkeys and they had grasping hands and feet.

These animals evolved into monkey-like animals, but remains of primates are scarce and the fossil record contains many gaps. Those few remains that have been found are of tree-living monkeys that are very similar to monkeys living today.

Where did humans probably evolve?

The early ancestors of humans were called hominids, and they appear to have evolved in Africa where many of their remains have been discovered.

The earliest remains of what were probably our ancestors are those of human-like apes called Australopithecus, which date back more than three million years. These creatures walked erect and looked similar to us, but their brain capacity was small. Several forms of Australopithecus have been found. All of them were much shorter than modern humans, and their teeth show that they had a vegetarian diet.

What remains of ancient humans have been found?

The first true human appeared around two million years ago in Africa. It has been named Homo habilis (‘handy man’) because it used primitive stone tools. It was still rather ape-like, however, and was soon replaced by Homo erectus, which looked very much like us. It had a much heavier jaw, bony ridges over the eyes and a sloped-back forehead. Homo erectus appeared about 1.6 million years ago. Only a few incomplete fossils of these early humans have been found, but their tools have been discovered in large numbers.

When did our ancestors begin to walk upright?

Some of the earliest remains of our ancestors are more than three million years old. They show very clearly that these creatures walked upright. The development of an upright posture, walking on two legs, is thought to have followed climatic changes. As the forest areas retreated our ancestors were forced to live on open grasslands. An upright posture would then be an advantage, because it allows an animal to travel more quickly. It also frees the hands for carrying food, babies and, eventually, weapons and tools.

When did the first modern human appear?

Modern humans appeared between 300,000 and 150,000 years ago, probably in Africa. The first ones were known as the Cro-Magnons, and they rapidly migrated throughout Asia and Europe. They did not reach North America until 12,000 years ago. Some of these ancient humans were the artists who made cave paintings showing extinct animals such as the mammoth and the cave bear. They were also almost certainly responsible for the extinction of many of these ancient animals, which quickly followed their migration into new hunting areas.

How closely related are we to modern apes?

Research shows that 99 percent of our genetic material is identical to that of the chimpanzee, which means that we not only resemble one another, but often share the same diseases. Some of the tropical diseases emerging from Africa are thought to have crossed over from chimpanzees to humans very recently. In addition to the physical resemblance, chimpanzees share with us the abilities to develop social systems and to communicate complex messages. Some of them have also developed the ability to make and use simple tools. We do know from fossilized teeth that there was once a huge ape called Gigantopithecus that was around three times the size of modern gorillas.

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Where can we see dinosaurs?

Most modern museums are very different from the early scientific exhibits of the 1800s. This was the time when popular interest in prehistoric life grew, and fossils of dinosaurs and other extinct creatures were first put on display to the public.

Today there are thousands of exhibits in natural history museums. Scientists have been able to reconstruct, in painstaking detail, how prehistoric creatures would have looked in real life. This gives us important information about the probable habits of these animals, instead of simply showing a mounted skeleton or fossil.

Wherever you live, take the time to look at the fossil remains in your nearest museum. By using your imagination, try to picture these extinct creatures as they once would have roamed the Earth.

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Could a giant sauropod walk on its front legs?

                   

                       Some fossil footprints of Apatosaurus caused puzzlement when scientists realized that they were the imprints of only the front legs of this vast reptile. They realized that the Apatosaurus must have been wading along in shallow water, pushing itself along with its long front legs while its hind legs floated clear of the muddy bottom.

                     At one time scientists thought that sauropods were far too large to have walked on land, and that they must have lived entirely in swamps where the water would support their weight. We now know this is incorrect, and that these giants were normally land-dwellers. In fact, they would probably have become stuck in soft mud due to their enormous weight, and preferred to live on dry land.

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How are fossils found?

Fossils are usually first revealed by the process of erosion, or by quarrying. They are found in sedimentary rocks which have been formed from mud and sand laid down millions of years ago. The remains of animals and plants are buried in the layers of rock. These sedimentary rocks are often buried deep beneath layers of other rocks that do not contain fossils. They are often exposed in sea cliffs, where the rock is worn away by the waves. Mining and quarrying also expose the deeper layers of rock, and many fossils are found in the loose material at the foot of rock faces.

Where are most dinosaurs discovered?

Most fossils have been found in Europe and North America, but they have also been found in most other parts of the world. In recent years, huge numbers of new and exciting fossils have been discovered in China, including huge new sauropods and several of the small dinosaurs which seem to have given rise to modern birds.

Fossils of mammals are not so old as those of the dinosaurs, and they are found in other regions. In particular, fossils of early man and the ancestors of mankind have been found in Africa.

 

Could we ever reconstruct an extinct animal?

We know that it is very unlikely that a dinosaur can be brought to life because its DNA is no longer complete. However, there are other possible ways of re-creating more recent animals.

Woolly mammoths are often found buried in the permanently frozen ground of Siberia and Alaska, and attempts have been made to extract DNA from the carcasses. It is hoped that this material could be inserted into the egg cells of a modern elephant, so a mammoth could be born again.

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When were the first dinosaurs discovered?

Many people must have noticed old bones in the ground, but they did not attract much attention. In the 1500s dinosaur fossils were thought to be the remains of animals or human giants that had perished in the Biblical flood.

The first proper scientific investigation took place after a huge pair of jaws was unearthed in the Netherlands in 1770. The jaws were identified by the great anatomist Cuvier, who recognized them as the remains of a marine lizard. The creature was christened ‘Mosaurus’. Many other fossil finds followed, and by 1830 five major groups of extinct reptiles had been recognized.

Why do palaeontologists disagree about dinosaurs?

Scientists have found very few examples of some of the more interesting and puzzling types of dinosaur. It is very rare to find a complete skeleton, and even rarer to find other clues, such as the animal’s last meal or traces of its fur or feathers.

As a result, palaeontologists often guess at the appearance of an extinct animal, based on a few clues and on similar living animals. This method leads to strong disagreements. For example, some experts say that dinosaurs must have been warm-blooded, in order to move quickly and to live in such varied habitats. Others insist that they were cold-blooded animals, like modern reptiles.

How are dinosaurs preserved and reconstructed?

It is rare that you can just pick up dinosaur bones. They are usually embedded in very hard rock, and it can take weeks of painstaking work to chip them out carefully and release the whole skeleton. Usually the bones were scattered before fossilization, so palaeontologists often have to excavate a wide area around the first finds in order to make sure that they have not missed any important parts. The remains may be taken to a museum still embedded in a block of stone. Once the rock is removed, the fossil bones are reconstructed on a metal frame. These bones have now turned to stone and so they are very heavy and brittle. As a result many museums make castings of the bone in plastic, which can then be jointed together for display.

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How did dogs evolve?

 

 

Dogs appear to have evolved from small mammals such as the mongoose, which appeared about 30 million years ago. This family proved very successful, and even the very early forms were similar to the modern dog. The early animals probably hunted in packs like modern animals of this group, enabling them to bring down large prey.

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