Oligocene epoch

33.9 to 23.1 million years ago

38 to 26 MILLION YEARS AGO

Around 35 million years ago, the continent of India meets up with the Euroasian continent. No sea separates the two at this time.

From 25 million years ago to the present, India will continue to push north against the larger continent to form the highest mountain in the world — Mount Everest. The presence of the Himalayan mountain range would help to change the climate to the west in places like the Middle East and northern Africa. Unfortunately it would not be to increase rainfall and so favour an increase in plant and animal life. Rather, it would be the opposite. Despite this, plenty of valleys containing underground springs and small streams would hold lots of vegetation. It is only when animals move away from these green pockets that the number of trees quickly thin out and with large patchy areas of dry grass, and in some places where no plants existed we can see the beginnings of deserts. (1)

As these geological events were happening, especially in the African continent, there came into existence two evolutionary branches from the Purgatorius primate. One species evolved into very primitive monkeys that were to lead to modern apes such as Chimpanzees, while the other became primitive ape-like primates living on open savanna country.

It should be noted that all the modern animals we see in the 21st century had their origins nearly 36 million years ago. In other words, if you could travel back in time and look around on the great continents of the world, you will notice many familiar animals of today (give or take a few minor changes in appearance and the presence of other creatures now extinct).

35 MILLION YEARS AGO

Africa pushes against Europe starting the building of the Swiss Alps.

28 MILLION YEARS AGO

The first direct evidence of what has been described as an apocalyptic comet colliding with the Earth has been found by scientists. The dirty snowball of ice and dust weighing at least 20 tonnes appeared over Egyptian skies and exploded in the atmosphere approximately 28 million years ago, raining down a massive shock wave of fire that killed everything in its wake over the Sahara desert below. The result of the shock wave was the melting of sand to a temperature of 2,000 degrees celsius forming a yellow silica glass that can be found today scattered over an area larger than the state of Delaware (or more precisely, a 6,000 square kilometres). Some of the glass was noticed by ancient jewellers and now adorn various man-made artifacts such as King Tutankhamun's scarab broach.

In addition to this, an Egyptian geologist Aly Barakat found a black pebble weighing 30 grams embedded inside some of this glass in December 1996. He sent the pebble to Marco Andreoli at the University of the Witwatersrand in South Africa. The discovery of this pebble turned out to be an absolute bonanza (and somewhat unusual in the sense that any evidence of comets colliding with the Earth tend to be microscopic dust moving high up in the atmosphere). On further analysis, the team of top notch South African scholars consisting of geoscientists, physicists and astronomers are hedging their bet that this pebble came directly from the comet.

"NASA and ESA [European Space Agency] spend billions of dollars collecting a few micrograms of comet material and bringing it back to Earth," said Professor Jan Kramers, a member of the scientific team involved in the analysis and who is the head writer for the article to discuss the discovery. "Now we've got a radical new approach of studying this material, without spending billions of dollars collecting it."

Of course, as with any scientific study, there is always going to be some debate as to whether the pebble is really part of the comet fragment (healthy skepticism keeps science well-balanced in its knowledge). As Ingo Leya at the University of Bern in Switzerland said:

"The problem is, we have little cometary material as a standard to compare with. Therefore, it is difficult to firmly conclude or exclude that this meteorite comes from a comet." (Grossman, Lisa. 'Black glass' could be first comet chunk found on Earth: New Scientist. 10 October 2013.)

Yet even Leya concedes the evidence that the pebble came from outer space is rather convincing to say the least. Among the interesting evidence to support the "extraterrestrial component" of the pebble according to Professor Kramers is the high carbon content, much higher (roughly 65 per cent) than are found in any meteorite sample (usually only 3 per cent). Also, the pebble contained isotope ratios of certain noble gases not found in meteorites or naturally here on Earth, leading the South African researchers to believe this pebble had to come directly from the comet itself.

The impact of the comet with the Earth's atmosphere and the subsequent explosion and shock wave had also helped to form tiny microscopic diamonds inside the pebble. A useful observation as not only would this prove the pebble was right in the middle of the action when the explosion occurred, but also scientists could determine the likely size and speed of the comet fragment (yes, the 20 tonnes is a conservative figure with the rest of the comet likely to have been much larger before it broke apart) thanks to our knowledge of how high the temperature and pressure had to be in order to form the hardest known substance in the universe (i.e., diamond).

Among the scientists involved in this discovery included Professor Jan Kramers of the University of Johannesburg (a geochemist and isotope geologist), and astronomer Professor David Block of South Africa's University of the Witwatersrand (known affectionately as Wits University). Further details are published in Earth and Planetary Science Letters towards the end of 2013.

25 MILLION YEARS AGO

A number of mammals have grown in size to become the largest of its type in all the continents of the world (including Australia). They would never reach the enormous size of those terrible reptiles called the dinosaurs, but compared to the animals of our times, these were big creatures.

For example, the ancestors of whales were at one time no bigger than a small horse with sharp teeth, four small legs and a tail, and had a thin fur on their skin. But they later grew into the biggest warm-blooded predators in the oceans weighing up to 60 tonnes and 4 times longer than a fully grown adult great white shark of this era.

Actually the shark species nearly 25 million years ago were at least twice as large as the biggest modern day great white sharks. Evidence for this observation can be found in the massive fossilised shark tooth collected from the Tasman sea floor in 2003 by CSIRO marine research scientist Dr Alan Williams during the joint Australia-New Zealand NORFANZ research expedition (2).

However, as food supplies dwindled in the cooler oceans of the world and along the shoreline, these massive predatory whales would eventually die out, leaving behind a handful of other whale species with better survival rates because of their greater reliance on alternative food sources such as plankton.