The earliest known bipedal vertebrate, eudibamus cursoris was a small parareptile. The sole specimen that has been found (in Thuringia, Germany) measured about 25 cm long – about the size of a house cat. Reconstructions of it give it an appearance resembling a cross between a tiny velociraptor and a modern iguana.
The sole specimen of it known to science was discovered in 2000 by a paleontological team including David S. Berman, Robert R. Reisz, Diane Scott, Amy C. Henrici, Stuart S. Sumida and Thomas Martens. The species is believed to have existed for a span of about five million years or so.
Everyone loves the dinosaurs. A lot of people – if the Jurassic Park films are to be believed – would like to see them come back. But without their extinction, we wouldn’t be here today.
Even now, it’s still not clear what exactly caused the extinction event – but the best known hypothesis is that of Luis and Walter Alvarez, which states that a meteoric or cometary impact caused a nuclear winter-like effect that altered the climate drastically, wiping out something like 75% of all species alive at the time. The effects were particularly felt by larger species – which included most dinosaurs.
In the wake of the event, now open evolutionary niches were occupied by mammals and birds, including our own ancestors.
Not actually true mammals, but instead mammaliformes, the members of the sub-class Allotheria are distinguished from other mammals chiefly by their dentition, which featured lower molariform teeth equipped with two longitudinal rows of cusps. Extant from the Late Triassic through to the Early Oligocene, the Allotheria were rodent-like animals in appearance.
They were widespread, found on all continents including Antarctica (which was considerably warmer in this era), and included in their ranks herbivores, carnivores and omnivores. Unfortunately for biodiversity, the last of them died out between 33.9 and 28.4 million years ago, give or take 100,000 years.
Australopithecus was an early proto-hominid that evolved in Eastern Africa around 4 million years ago. It consisted of a number of sub-species: A. anamensis, A. afarensis, A. sediba, and A. africanus; and two more sub-species whose genus is disputed: A. robustus and A. boisei. Over the course of two million years or so, the various Australopithecenes ranged across Eastern and Southern Africa.
The Australopithecines evolved about 2 million years after the split between the ancestral roots of humanity and chimpanzees (our closest relative), and one or more of the various sub-species of Australopithecus is likely to have been the progenitor of the Homo Genus, to which modern humanity (homo sapiens sapiens) belongs.
The earliest species to evolve in the genus homo was Homo habilis, which is believed to have evolved in Africa from Australopithecene ancestors (although which of several species of australopithecus was the direct ancestor is not known). The genus homo would go on to become the most successful species in the entire history of the earth, until it created a global ecological catasprophe in the early to mid twenty first century, which destroyed all the members of that genus, and almost every other genus above the size of bacteria.
(By the way, if you’re reading this, you’re either a homo, or an extraterrestrial intelligence that’s very tolerant of our immaturity.)
(Man, I love that pun.)
It’s unclear exactly what killed the mammoths off, although there are two leading contenders: the end of the last Ice Age made climates generally warmer (although the last ice age ended several thousand years before the extinction was complete) and predation – the predator in question being, of course, us.
At one point, mammoths were found across most of the northern reaches of Europe, Asia and America, in several different species, but bit by bit, these were hunted to extinction. The shrinking of their optimal habitat as the ice retreated probably made the hunting easier, but their extinction was a certainty as soon as our ancestors developed a taste for mammoth-meat.
The last known population of mammoths, that on Wrangel Island in the Arctic Sea to the north of Chukotka (the easternmost part of Asia), became extinct in about 1650 BCE, having survived their relatives on St Paul Island, Alaska, by about 1100 years.