00:00A fascinating and at least unexpected discovery emerged among the rocks of the Dika Valley, in Peru.
00:07The bones of a prehistoric whale, Perusetius Colossus, which lived nearly 40 million years ago.
00:14Initially, these massive bones and unusual shapes did not arouse much interest,
00:19because they were thought to be simple gigantic rocks.
00:22Of course, this hypothesis could be intriguing,
00:25but things took a different turn when researchers realized
00:28that they were facing the remains of a colossal marine animal that once roamed the coasts of Peru.
00:33In addition, this whale would probably be the heaviest being to have ever existed.
00:38Sorry, blue whale, we know you did everything to get your place at the top.
00:42With a length of more than 30 meters and a weight exceeding 200 tons,
00:47it deserves its status as the largest animal on the planet.
00:50However, it seems that its reign is coming to an end.
00:53It is time to give the title to a new challenger, and this one is truly titanic.
00:59This creature of the oceans was undoubtedly shorter than the blue whale,
01:03but much heavier, with a mass estimated between 93 and 370 tons.
01:09If calculations point to the upper fork,
01:12Perusetius could become the largest animal ever known on Earth.
01:16This impressive weight is explained by extraordinarily dense and thick bones,
01:21a trait that is still observed today in species such as the lamentans or some of the first cetaceans.
01:26These dense bones are a considerable asset for marine mammals,
01:30because they allow them to remain submerged most of the time.
01:34But an excess of weight can be problematic.
01:36A body too heavy would tend to sink permanently,
01:39forcing the animal to spend a considerable amount of energy to go back to the surface.
01:44To avoid this, marine mammals must have sufficiently lighter tissues,
01:49such as muscles or fat,
01:51to guarantee their buoyancy while minimizing their efforts.
01:55Scientists do not have a complete skeleton,
01:57which complicates the evaluation of the size of the animal.
02:00However, they used the ratio between heavy bones and lighter tissues
02:05observed in other marine mammals to estimate the total weight of this huge prehistoric whale.
02:10These fossils were discovered about 13 years ago,
02:13and researchers spent the next 10 years extracting the whale from the rock.
02:17The analysis of its anatomy and age revealed that it was related to the basilosaurus,
02:23a whale with a long muzzle filled with sharp teeth,
02:26and an elongated body, evoking that of a eel.
02:29Even if Perusetus was not larger than the blue whale,
02:32it was no less than a giant reigning over ocean depths.
02:36Contrary to modern whales,
02:38it is plausible that this creature was a predator attacking large prey.
02:44This discovery also upsets our understanding of the evolution of whales.
02:48Researchers previously thought that these majestic creatures
02:51had reached impressive sizes about 5 million years ago
02:55when they began to consume a large amount of small prey.
02:58However, here is the proof that gigantic whales existed long before.
03:03However, it remains to be clarified how this whale found enough food to meet its needs.
03:09In addition, it remains difficult to determine precisely the diet of this ancient creature.
03:15With its imposing size and its slow swimming,
03:17it was probably looking for its food in shallow waters.
03:21It was probably feeding on crustaceans,
03:23swamps or other small animals buried in the sand.
03:26A hypothesis suggests that it was a carnivore,
03:29feeding on the remains of animals found on its way.
03:32It is not uncommon to discover fossils of marine animals in the deserts,
03:36because many of these areas were once submerged.
03:39The Sahara, for example, was, 50 to 100 million years ago,
03:44a shallow sea called the Trans-Saharan Maritime Way.
03:48If this region is now arid,
03:50the inhabitants of these places were aware of their aquatic past,
03:53because they often found old shells there.
03:56The sea reached a depth of about 50 meters,
03:59an ideal depth for swimming.
04:02Some could compare this region to today's Puerto Rico,
04:05with its abundance of sun and its shallow waters.
04:09The mangrove forests were widespread there,
04:12just like the seabed covered with molluscs,
04:14such as snails and squirrels.
04:17The marine sediments deposited after the drying of the sea
04:20are full of varied fossils.
04:22The creatures inhabiting this ancient underwater world
04:25had a less engaging appearance
04:27and were much more imposing than their current descendants.
04:30A normal-sized human being
04:32would hardly constitute an anchor for these giants,
04:35far from a complete meal.
04:37Generally, when an animal settles on a small island,
04:40it can reach a size much larger than that of its continental peers.
04:44This phenomenon, known as insular gigantism,
04:48is explained by the increased presence of resources
04:51or the reduction of the number of predators on the islands.
04:54Perhaps a similar phenomenon occurred in the Trans-Saharan Maritime Way.
04:58Although it is not an island,
05:00the incessant movements of the waters
05:02have formed small, isolated pockets.
05:04The specific conditions prevailing there
05:06have probably favored the growth of certain species.
05:10Thus, we find creatures such as sea snakes
05:13and colossal cichlids,
05:15as well as other fish that have disappeared today.
05:17Among them, a pycnodontiform was distinguished
05:20by its powerful jaws,
05:22which it used to crush shells
05:24and attack hard prey.
05:26The identity of these animals
05:28testifies to their role as predators in this ecosystem.
05:31Their diet has evolved over time,
05:33like some modern piranhas.
05:36But the competition to dominate the food chain was fierce,
05:39especially against predators of size
05:41such as sharks, crocodiles
05:43or even ancient ancestors of elephants.
05:46The Sahara has gone through several phases in its history.
05:49If you had a time machine
05:51and you visited what is now
05:53the largest hot desert in the world,
05:55as it was about 6,000 years ago,
05:57you would not be confronted
05:59with a sea of burning sand.
06:01On the contrary, you could enjoy
06:03a pleasant walk through a luxurious landscape.
06:06The inhabitants of this region, in the past,
06:08did not leave any paint on the walls of the caves
06:11depicting camels, dunes or scorpions,
06:14these characteristic elements of the current Sahara.
06:17Instead, they drew crocodiles.
06:20These illustrations offer additional proof
06:23that at one time, the Sahara was full of water and vegetation,
06:26enough to accommodate these imposing and formidable reptiles.
06:30About 3 billion years ago,
06:33the earth was probably almost entirely covered with water.
06:36Today, the oceans cover about 71% of the earth's surface,
06:41but it seems that at that time,
06:43it looked like a vast oceanic world,
06:45without a real continent,
06:47only sprinkled with a few islands.
06:49Scientists have examined particular rocks
06:52in Western Australia,
06:54formed in a deeply submerged environment
06:57called a hydrothermal source system.
07:00To better understand,
07:02it is necessary to mention two types of current oxygen,
07:04O-16 and O-18.
07:07The latter, heavier thanks to its additional neutrons,
07:10evaporates less easily.
07:12By analyzing old marine foundations,
07:14researchers have discovered a significant proportion of O-18,
07:18much higher than those observed in the current oceans.
07:21This has led them to conclude that in the past,
07:24the earth had fewer emerging lands than today.
07:27Australia, once a green place
07:29home to large animals and vast tropical forests,
07:32is today the ideal place to conduct this type of study.
07:36Over time, this land has become more arid,
07:39and deserts such as the Great Victoria Desert have formed.
07:42Tropical forests, on the other hand,
07:44have gradually reduced to the ends of the continent.
07:48This phenomenon, known as desertification,
07:51occurs when lands formerly fertile
07:54and adapted to agriculture
07:56turn into deserts.
07:58If natural climate change contributes to this evolution,
08:02human activities, such as mining,
08:05intensive agriculture or urban construction,
08:08also play an important role in this transformation.
08:12When lands become desert,
08:14this poses many problems.
08:16They can no longer produce food,
08:18drinking water becomes insufficient,
08:21and animals lose their natural habitat.
08:24To fight this phenomenon,
08:26many countries have adopted a plan.
08:28This aims to collaborate with farmers
08:30to restore degraded lands,
08:32manage water more efficiently
08:34and preserve productive areas
08:36in order to improve living conditions on our planet.
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