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This skull belonged to Homo erectus, the first human species to leave Africa about 2.1 million years ago. When Homo erectus migrated from Africa, the climate in the northeast of the continent was wetter and more lush than it is today, according to a new study. Climate cycles combined to form green corridors, which our early ancestors likely took advantage of during migration. Credit: Mizmareck / FlickrThe green corridor that runs through the Sahara desert emerged just as our ancestors migrated from Africa. This is shown by the following new research. Aarhus University.About 6 million years ago, something amazing happened in the deep forests of eastern Africa. Chimpanzees, our closest relatives in the animal kingdom, evolved in one direction, while our first ancestors continued to evolve in another direction.Over the next millions of years, the differences between early humans and chimpanzees grew larger and larger. Our ancestors climbed down from trees and began walking upright on two legs, freeing their hands to use tools.This was the beginning of a development that would end with humanity conquering most of the Earth.About 2.1 million years ago, the first humans, Homo erectus, migrated from Africa. The journey took them through northeastern Africa and the Middle East (areas today mostly covered in desert), and on to Europe and Asia.Black dots in the Mediterranean indicate where sediment cores were collected. This area is supplied with terrestrial material from northeastern Africa, but the landscape and vegetation changed under the influence of the African Wet Period.Credit: Nature Communications Earth and EnvironmentFor years, researchers have speculated about how Homo erectus was able to traverse the arid, unforgiving desert with no food, water or shade.New research from Aarhus University suggests Homo erectus may not have been walking through deserts when it left Africa, says Rachel Lupien, one of the researchers who contributed to the new results. explain.“We know that there are repeated periods of changing climate in the Sahara Desert. We call this phenomenon the “Green Sahara” or the “African Wet Period.” During the green season, the desert shrinks significantly, transforming into a landscape resembling the East African savanna we know today,” she says, adding:”Our results show that the Sahara was greener at the very time Homo erectus first migrated than at any time in the 4.5 million years we studied. most likely could have walked through the green corridor outside.”the race that conquered the worldThe first humans were seed Homo erectus appeared in eastern Africa more than 2 million years ago.Homo erectus was the first hominin to learn how to carve an ax out of stone. These axes were probably used as weapons for killing prey and cutting meat from bones. They were probably also the first to learn how to control fire.Homo erectus was slightly shorter than modern humans, but more muscular. They had wider hips and elongated skulls. Additionally, their brains were significantly smaller, about half the size of ours.For more than 1.5 million years, Homo erectus lived and spread throughout most of the planet. From Africa, through Europe and Asia, across the Strait of Malacca to some islands in Indonesia. This made Homo erectus the longest-lived human species. We, Homo sapiens, evolved about 300,000 years ago.sauce: natural history museumThe ocean floor reveals past climateThe Sahara Desert as we know it today is in one of its dry seasons. The duration of these periods varies, but approximately every 20,000 years, the continent goes through both wet and dry cycles. These rainy seasons are what Rachel Lupyan has called “Africa’s wet seasons.””How wet it gets during the wet green period varies. In fact, there are two other cycles involved, one lasting 100,000 years and one lasting 400,000 years. So , over a period of 100,000 years, the wet period will vary, becoming wetter or drier than usual. The same is true for 400,000-year intervals,” says Rachel Lupyan.But how do we actually know what Africa’s climate was like hundreds of thousands of years ago?The ocean floor tells us, and for this very reason, we actually already know a lot about past climates, she explains.”Using core samples from the Mediterranean Sea, we can learn what the climate was like millions of years ago. Layers of sediment have formed on the ocean floor, and these layers contain Small molecules can tell us a great deal about what the climate was like in the past.”Substances that make leaves shineOver time, material ejected from North Africa forms a new layer on the ocean floor that slowly descends across the ocean. Therefore, the buried ocean floor acts as a kind of logbook that can tell us what the climate was like in the past.The layer has a set of biomarkers that store information about past climate. One of these markers is a set of molecules that plants use to protect their leaves. They are also called leaf wax, explains Rachel Lupyan.”Waxes coat trees, bushes, and blades of grass, making them shine. When a plant dies, most parts of the plant decompose rapidly, but wax molecules can survive for long periods of time. That is why such molecules are often found in sediments that are millions of years old.”The chemical composition of wax molecules can tell us what the climate was like when that layer formed. For example, the hydrogen molecules in the wax can give some information about how much precipitation there was.“Water contains hydrogen, so hydrogen can be used to circulate water. Water on Earth contains both regular hydrogen and deuterium (deuterium). “When it rains a lot, plants can absorb relatively less deuterium, but when it’s dry they absorb more,” she says.Carbon holds important knowledgeRachel Lupyan and her colleagues could tell by the amount of deuterium in the wax of leaves during wet and dry times. But hydrogen doesn’t tell us anything about which plants grew in humid climates.But it is present in the carbon atoms found in leaf wax, she explains.“There are two main types of plants. We also refer to them as C3 and C4 plants,” she says.”About 90 percent of all plants are C3 plants. They live in most areas of the earth, except in extremely dry or very hot regions. C4 plants, on the other hand, They specialize in surviving in areas with high temperatures.”C3 and C4 plants produce leaf wax containing different amounts of heavy carbon, allowing researchers to distinguish between them in samples. In this way, you can “read” which types of plants were most dominant at the time.”At the time Homo erectus migrated out of Africa, more C3 was detected in samples than during any other humid period in the past 4.5 million years. It shows a change to grassland or savannah,” she says.3 types of photosynthesisBroadly speaking, there are three different methods in the plant kingdom. photosynthesis. There is a C3 plant, a C4 plant, and his third variant called the CAM plant.90% of all plants are C3 plants, 6% are CAM plants, and only 3-4% are C4 plants. However, this is not the case in Africa. In Africa, vast grasslands have a much higher proportion of C4 plants.Differences among plants are due to different coping strategies when moisture in the air or soil is limited.When it gets too dry, C3 plants close the small stomata in their leaves and absorb CO2. When the hole closes, the plant can no longer photosynthesize and begins burning stored carbon, expelling water and carbon dioxide. If this continues for too long, the plant will die.On the other hand, C4 plants can photosynthesize even in dry conditions. Even though the stomata are closed, they continue to convert CO2 into energy. They can do this with the help of a molecule with four carbon atoms, which gives the plant species its name. CAM plants use his third method and can cope even with drier regions.Wheat, oats, rice, and sunflowers are examples of C3 plants. His known C4 plants are corn, sugar cane, and amaranth, while succulents, cacti, and pineapple are his CAM plants.sauce: khan academy, biology dictionary and rex.dkGreenest 2.1 million years agoGreen periods in Africa, similar to ice ages in northern latitudes, are caused by small fluctuations in the Earth’s orbit around the sun. Geologists call these fluctuations Milankovitch cycles.And two of these changes in particular will play an important role as the Sahara desert receives more rainfall, explains Rachel Lupyan.”The Earth wobbles a bit in its orbit around the sun.…

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Source: scitechdaily.com