Elephants

Elephants, the largest land animals alive today!

Of the order, Proboscidea. Last remnants. Descendants of mammals that lived millions of years ago.

"Today there are three living elephant species found on Earth: the Asian elephant, the African forest elephant and the African savanna elephant."

Early proboscideans that lived in Africa were slow-evolving with little diversification.

Once the Afro-Arabian Plate collided into the vast Eurasian landmass, an important migratory corridor was formed, which allowed the species to explore new habitats in Eurasia and then into North America. This was via the land bridge which sporadically connected Siberia to Alaska and is now submerged under the Bering Sea.

Over the past 20 million years, the global climate changed frequently and dramatically. Provided with new challenges and habitats, proboscideans that expanded from their range in Africa evolved 25 times faster than the cousins they left behind. This resulted in a variety of forms, with three to four different proboscidean species coexisting in one space. This richness of giant herbivores was unlike anything in today's ecosystems.

But from about six million years ago, the diversity in proboscideans started to decrease following the harsh cooling of Earth. Only the most ecologically versatile proboscideans survived.

The most extreme example would be the wooly mammoth, which had thick, shaggy hair and large tusks for retrieving vegetation hidden under thick snow.

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"The very earliest proboscidean would have been the size of a French poodle. It would look something like a river rat. No big ears. The nose was at the very front of the face," Sanders said. "They didn't have trunks or tusks. Those were features acquired over time."

For more than half of its 60 million years, proboscideans lived in isolation on the Afro-Arabian supercontinent, the landmass that existed before the African continent split from the Asian continent.

By the Oligocene, between 25 million to 30 million years ago, 11 more families emerged. More than 6 feet tall and 4,500 pounds, Barytherium was the first immense-sized proboscidean.

Gomphotheres emerged around 30 million years ago and dominated the continent until about 8 million years ago, into the early part of the late Miocene. Similar in size to the Asian elephant, some genera of gomphotheres had elongated lower jaws while others more resembled present-day elephants. Our modern-day elephants descended from one of these gomphothere lineages.

When the Afro-Arabian continent collided with the Eurasian continent, the Order bloomed. Mammoths and mastodons grew long fur and ranged through Siberia and North America. Tetralophodons, proboscideans with four tusks, lived throughout Europe, Asia and Africa. Dozens of others tested their fate nearly all over the world. Ultimately, numerous proboscidean families rose and fell and rose again over tens of millions of years.

More than 180 families have been described, and are now extinct. Now, just three species of elephants remain: the African forest and savannah elephants, and the Asian elephant.

As to the role of humans. Yes, for modern elephants. But for earlier ones of the above order:

Early humans became effective hunters of large animals around 1.5 million years ago. The team's analysis shows the final proboscidean extinction peaked much earlier, however, at around 2.4 million years ago.

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The animals are a keystone of African faunas, ecologically dominant and vital, and the oldest continuously surviving African mammals who bear offspring by growing a placenta. There is no other mammal group in Africa that researchers can trace back as far

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About Proboscidea:

This classification was based on the defining feature of this order: the proboscis, or trunk, which is a remarkable combination of the nose and upper lip. It could perform the functions of breathing, olfaction, touch, manipulation and sound production. 

The trunk of an Asian elephant that we see today is a marvel of considerable evolution, with approximately 1,50,000 muscles. It can perform fine motor skills like delicately picking up small items like peanuts as well as gross motor skills like breaking off thick branches of a tree.

For comparison, there are 34 muscles in human hand. (Another source says elephant trunks have just 40k more muscle group than human hand(

The elephant trunk is similar to other boneless organs in nature such as the octopus arm, and the human tongue and heart. These organs are composed of a tightly packed array of muscle and connective tissues. They are known as muscular hydrostats and are composed of interdigitated muscle fibres arranged in three dimensions. They thus lack the discrete muscles of rigid skeletal support systems. The elephant trunk is the largest muscular hydrostat on land, making it subject to substantial gravitational forces.

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In terms of sensitivity, it is often said that an elephant's trunk is one of the most sensitive organs in the animal kingdom, capable of detecting touch at a level of precision that would rival the sensitivity of human fingertips, but with a far greater range of tactile and environmental information.

 

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The elephant trunk and human hand, though serving similar functions, have vastly different muscle structures and innervation. The elephant trunk, a muscular hydrostat, contains a staggering number of individual muscle units (around 40,000), compared to the human hand's approximately 30 muscles. This difference in muscle count reflects the trunk's ability to exert tremendous force and dexterity, allowing it to lift heavy objects and pick up tiny items with precision

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An elephant’s trunk is incredibly sensitive. It is covered with specialized tactile receptors, and these sensory organs can detect even the faintest vibrations, temperatures, and pressures. Elephants can use their trunks to sense:

Surface texture: They can detect the smallest textures, from the rough bark of a tree to the smooth surface of a rock.

Subtle vibrations: They can feel seismic waves or vibrations in the ground, which helps them communicate with other elephants over long distances.

Chemicals: The trunk is also equipped with a keen sense of smell, allowing them to pick up chemical signals from their environment, including water sources or the scent of other elephants.

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So far, about 175 species and subspecies of proboscidea are known to have existed and are classified into 42 genera and 10 families.

And only 3 species of the order are alive today.

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Food

In terms of dietary preferences, early proboscideans mainly exhibited browsing behaviour, while grazing became the trend in later periods. Grazing and browsing are two feeding strategies observed in herbivores and are distinguished by the different types of vegetation they consume. Browsers primarily feed on leaves, fruits of tall woody plants, shoots, and shrubs while grazers eat grass and other vegetation found in close proximity to the ground. 

Wild African elephants are voracious eaters, consuming 180 g of food per minute. One of their methods for eating at this speed is to sweep food into a pile and then pick it up.

    Wild elephants browse and graze for up to 18 h per day, consuming over 200 kg of vegetation per day. Thus, on average, an elephant eats 180 g of food, or the weight of two corn cobs, per minute. 

Elephants use a different mechanism: they squeeze the particles together, jamming the grains which cause the pile to solidify. 

See interesting following:

Although the elephant trunk lacks bones, the formation of a joint mimics a common vertebrate strategy to reach out and grab objects. The human upper limb, for example, has seven degrees of freedom. These degrees of freedom make it possible to reach out into arbitrary points in three-dimensional space and grab objects, as well as perform twisting motions in all three directions. An animal with more joints has more degrees of freedom to accomplish tasks. But these joints also provide challenges too, as the animal must search through more potential solutions. This is why appendages without bones, such as the elephant trunk and octopus arm, have both demonstrated the formation of joints. The octopus forms a joint like the elbow only when retrieving food [20,21]. Our study shows that the use of joints might be more common than once thought.

 

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Teeth

The elephants of today have a very unique and complex dentistry with their teeth placed horizontally (like a conveyor belt) instead of vertically, like in humans. New sets of molars develop at different stages in their lives to prevent all their teeth from wearing down due to the amount of chewing and grinding that they indulge in every day.

A reflection on size:

Land mammals kept getting larger for 35 million years after the dinosaurs were wiped off the planet, then hit a plateau of 15 tonnes around 30 million years ago.

The first comprehensive study to compare the maximum size of fossils around the world shows how the extinction triggered a growth spurt in the mammals that were left to take over the continents. It reveals that land mammals around the world responded the same way to the death of the dinosaurs 65 million years ago.

An intersting take, or a perspective on evolution (response to environment)

The fossils show how mammals – which initially weighed in at only 10 to 100 grams – ballooned and eventually reached a maximum of 17 tonnes some 25 million years later. The largest one, Indricotherium transouralicum – which is also the largest mammal to ever walk the earth – was a hornless rhinoceros-like herbivore that stood about 5.5 metres tall at shoulder level.

“Basically, the dinosaurs disappear and all of a sudden there is nobody else eating the vegetation,” says co-author Jessica Theodor of the University of Calgary, Alberta, Canada.

All of the largest mammals were plant-eaters. “It’s more efficient to be a herbivore when you’re big,” says Theodor.