About 180 million years ago, mammals arose from a reptile-like lineage about the same time as true dinosaurs. About 80 Million years ago, the genetic linage of elephants split from primates. The tree shrew is considered our nearest common ancestor.It is believed that 50-60 million years ago, Moeritheriums, approximately the size of current day pigs, were the roots from which the proboscideans evolved. Based on both morphological and biochemical evidence, it is generally agreed that the manatees, dugongs, and hyraxes are the closest living relatives of today’s elephants. This is incredible given the vast difference in sizes, external appearance and the fact that these animals occupy completely different habitats.The order under which Elephants are classified is the Proboscidea. This means animals with trunks=proboscis.Over the course of evolutionary history, it has been estimated that there have been about 352 species of Probscideans. The creatures of this order have inhabited every continent except Australia and Antarctica. All but two (the African and Asian elephants) have died out.
Proboscidean Biology and History
Proboscideans are an order of mammals that includes elephants and their extinct relatives like mammoths and mastodons. They are characterized by a trunk (proboscis) and specialized teeth. Their history spans millions of years, with the earliest proboscideans emerging in Africa around 60 million years ago.
Early Proboscideans
The first proboscideans were small, pig-like creatures that lacked a true trunk.
Diversification
Over time, proboscideans diversified, evolving into a wide range of species with various sizes, shapes, and adaptations.
Three major radiations of proboscideans are recognized: the early Paleocene/Eocene diversification, the Miocene expansion outside Africa, and the late Miocene/early Pliocene emergence of Elephantidae (including modern elephants).
Many proboscidean species went extinct during the Pleistocene epoch, likely due to climate change and/or human hunting.
Global Distribution
Proboscideans once thrived on all continents except Antarctica and Australia. Today, they are only found in Africa and Asia.
Biology
- Proboscis - The proboscis is a unique feature of proboscideans, used for grasping food, water, and objects, as well as for communication.
- Teeth and Tusks - Proboscideans have specialized teeth for grinding vegetation, and many species also have tusks (enlarged incisors) used for various purposes.
- Size and Weight - Proboscideans are among the largest land mammals, with some species exceeding 16 tonnes in weight.
- Diet - Proboscideans are herbivores, feeding on a variety of plants and grasses.
- Social Behavior - Elephants, the only living proboscideans, exhibit complex social structures and strong family bonds.
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A recent study analyzing 34 new mammoth mitogenomes, spanning over a million years, reveals a complex evolutionary history, including long-lost genetic diversity and shifts in population size and movement. The study, published in Molecular Biology and Evolution, provides insights into how major demographic events during the Early and Middle Ice Age shaped mammoth diversity.
Key findings
- Complex genetic diversity - The study challenges the idea of a linear lineage, suggesting that mammoths emerged from a complex web of genetic diversity.
- Deep-time genetic data - Analysis of mitogenomes from the Early and Middle Pleistocene periods (1.3 million to 125,000 years ago) provides a unique glimpse into past genetic diversity.
- Siberia as a source - The study indicates that Siberia may have been the original homeland for the main mammoth lineages.
- Population shifts and extinction - Shifts in population size and movement appear to have played a key role in the emergence, spread, and extinction of different genetic groups.
- Three genetic groups - In the Late Pleistocene, mammoths fell into three genetic groups, all of which shared a most recent common ancestor around 780,000 years ago, potentially aligning with the appearance of the woolly mammoth.
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Please explain the oxford article mentioned in the link below. Please exclude all mention of research methodology: A Million Years of Mammoth Mitogenome Evolution
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