Exploring Evolutionary History: The Story of the Human Body

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[00:00:14] Today we will unlock the book the story of the human body.

[00:00:18] Within Running Clubs, Barefoot Running has become a trending activity in Europe and the US for a while.

[00:00:24] Why should we run Barefoot?

[00:00:26] Why is such a weird activity popular?

[00:00:29] In essence, it actually involves knowledge related to human evolution.

[00:00:35] The so-called Barefoot Running freeze the feet from the shackles of shoes and socks.

[00:00:40] The muscles of the souls, ankles, calves, and thighs are thus able to perform their respective

[00:00:45] duties to complete their inherent task when running. Many studies prove that walking barefoot

[00:00:51] is more conducive to the health of foot joints and muscles than walking with shoes,

[00:00:55] and dramatically reduces damage to the knee joint from running.

[00:01:00] Why is this case? If shoes were invented by humans to provide comfort and safety,

[00:01:05] why do they create health problems?

[00:01:08] In a broad sense, the reason lies in the direction of our body's evolution.

[00:01:13] Scientists estimate that the earliest hominins arose around 6 million years ago,

[00:01:18] and it took that much of a time for human evolution to achieve the stage of modern humans.

[00:01:24] During most of this span of time, humans walked barefoot, so our foot structure and walking

[00:01:29] style have adjusted for walking in such way. Specifically, our souls have developed a rich and

[00:01:35] extensive neural network that can detect discomfort in our feet when walking.

[00:01:40] As a result, we naturally and continuously adjust our posture while walking in order to

[00:01:45] avoid damage to the joints. However, wearing shoes impair such ability.

[00:01:50] With a history of barely more than 45,000 years, wearing shoes is a new fashion that only appeared

[00:01:58] relatively recently compared to the 6 million years of human evolution. Hence, as far as our bodies

[00:02:04] are concerned, wearing shoes is still a new territory. Our feet have yet to totally adapt to this

[00:02:10] new environment, which has led to a series of problems. Studies have shown that foot diseases such

[00:02:16] as flat foot and berryberry can be easily induced by placing feet in humid, deoxygenated,

[00:02:22] and closed conditions over an extended period such as in a shoe.

[00:02:27] As a matter of fact, in the wake of changes in our living conditions, more and more diseases

[00:02:33] have emerged due to our bodies inability to adapt to the new environment. These diseases are also

[00:02:39] known as mismatched diseases. For example, high blood pressure, diabetes, coronary heart disease,

[00:02:46] cancer, depression, and anxiety. So, what are the environmental changes that make us vulnerable to

[00:02:54] the mismatched diseases? Is there a way for us to prevent and treat them? The book the story of

[00:03:00] the human body will tell you all the answers. Seeking to understand the causes,

[00:03:06] preventions, and cures of mismatched diseases, this popular science book begins with a modern

[00:03:11] context and then looks back on the history of human evolution. In this book, you will get to know

[00:03:17] the evolutionary origins of all our body parts, and why they developed as they did,

[00:03:22] and in what environment they are formed. Daniel E. Lieberman is a professor of human

[00:03:28] evolutionary biology at Harvard University. His field of research spans multiple academic disciplines,

[00:03:35] such as paleontology, anatomy and physiology. He has made remarkable achievements, especially in

[00:03:42] the field of human brain evolution. Lieberman received the Everett Mendelssohn Excellence in

[00:03:48] Mentoring Award in 2009 in Harvard College Professorship from 2010 to 2015. For years, he had been

[00:03:55] thinking of one question, how did the human body evolve into its current form? This book the story

[00:04:01] of the human body is as attempt to answer this big and complicated issue to the best of his ability.

[00:04:08] Next, we will uncover for you the best bits from the book in three parts. Let's take a look at

[00:04:14] the secrets of our body's evolution. Section 1, how the environment shaped the human body.

[00:04:21] Section 2, the rise of mismatched diseases driven by the agricultural revolution and the industrial.

[00:04:28] Section 3, the causes and preventions of mismatched diseases.

[00:04:34] The evolution from the earliest hominins to the present human being can be roughly divided

[00:04:39] into five stages, each stage is characterized by a crucial transformation that resulted from adaptation

[00:04:45] to the environment, which led to the development of the human body as we know it today. Let's check

[00:04:51] out the first transformation, the evolution into upright bipeds. Sahelinthropist Chaudences

[00:04:58] bororin-tu-genensis, an artipithecus cadaver where the earliest hominins six million years ago.

[00:05:04] At that time, the global climate cooled considerably. The cooling process lasted over millions

[00:05:11] of years with fluctuations between warmer and colder periods. This led to the shrinkage of

[00:05:16] rainforests and the expansion of woodland habitats. This significant climate change altered the

[00:05:23] living conditions of the hominins. At the same time, it created food shortages for them.

[00:05:29] As a result, the body of the hominins had to undergo a transformation to adapt to these changes.

[00:05:35] The most prominent change they made was adjusting to walking upright.

[00:05:40] Due to the shrinkage of rainforests, our ancestors had no choice but to walk further in search

[00:05:45] for habitat and food. Standing on both feet could make it easier for them to pick certain fruits,

[00:05:51] and it was more energy efficient. Studies shows that given the same energy consumption,

[00:05:56] a chimpanzee can only walk two or three kilometers per day, while a human being can walk eight to

[00:06:02] 12 kilometers. This is determined by the body structure and walking posture. Studies on fossils

[00:06:09] from six million years ago indicate that a ruin-tu-genensis had already developed feature suitable for

[00:06:15] walking upright. For instance, they developed a large hip joint, a wider femur, muscles at the arch

[00:06:22] and the foot used for propulsion, an esch-shaped spine, and so on. These adaptive changes enabled

[00:06:28] them to acquire more food than their counterparts, and ensure a higher survival rate.

[00:06:34] The second stage of evolution was mainly a result of coping with food shortages.

[00:06:39] Four million years ago, with the expansion of open woodland and savannah habitats,

[00:06:44] there were fewer and fewer edible wild fruits available. Because of the fruit crisis, our human

[00:06:50] ancestors began to feed on leaves, plant stems, herbs, and bark. In order to chew hard and tough foods,

[00:06:58] their teeth and faces underwent adaptive changes. One example is Australopithecus. Their teeth

[00:07:05] are not only broad and thick but also flattened. They have much smaller, shorter, and less dagger-shaped

[00:07:12] fangs than chimpanzees. Big and full teeth are better suited for tough and hard foods. Also,

[00:07:18] they have evolved huge chewing muscles, wide cheekbones, and upper and lower jaws. These features

[00:07:25] produced powerful bites that simultaneously displaced their cheekbones outward, making their

[00:07:30] faces wide as they were long, causing it to appear large. The era of the Australopithecus was a

[00:07:37] crucial transition period in human evolution. They reduced their dependence on fruits and time-span

[00:07:43] on trees. They became more accustomed to walking on both feet, which laid the foundation for

[00:07:48] the third stage of evolution. The third stage of evolution took place around two or three million

[00:07:55] years ago. When the Earth entered the early ice age, and again, food became scarce.

[00:08:01] Natural selection prefers a revolutionary and more thorough solution to a changing habitat,

[00:08:07] which is why our ancestors left foraging behind and started hunting and gathering.

[00:08:13] The new behaviors included not only collecting tubers and other plants, but also eating more meat,

[00:08:19] using tools to harvest and process food, working in close cooperation with others,

[00:08:24] sharing food, and so on. Food sharing was an iconic feature of the hunter-gatherer period.

[00:08:32] These changes allowed Australopithecus to gradually evolve into the genus Homo,

[00:08:36] and to acquire a body close to that of modern humans. People from this period are called Homo erectus.

[00:08:44] The most apparent adaptive change that happened at this stage was the elongation of legs.

[00:08:49] The backbone and joints of the leg bones also transformed. These changes allowed our ancestors

[00:08:55] to run longer to catch up with animals. In contrast, apes usually walk no more than 3 kilometers a day.

[00:09:04] Running for a long time requires lower body temperature, so the body hairs of the hominins at

[00:09:09] that time became thinner and the hair follicles degenerated. They also developed extra

[00:09:14] sweat glands for lowering their body temperature during vigorous running, and a unique outer nose

[00:09:20] that plays an important role in thermoregulation by generating turbulence in the air inhaled through

[00:09:25] the inner nose. Furthermore, during this period, humans' gluteus maximus began to develop for

[00:09:32] running long distances, as well as the semicircular canal of the inner ear to maintain balance.

[00:09:38] It could be said that the third stage of evolution was a crucial step in the evolution of hominins from

[00:09:43] an ape to a human being. In the fourth stage, the body of hominins evolved further as it developed

[00:09:50] an energy conversion system to provide enough energy to the brain. This physiological system enlarged

[00:09:57] the human body, thickened layers of fat, and also caused the body to grow relatively more slowly.

[00:10:04] We have learned that in the third stage, Homo erectus learned to cooperate and share, thus

[00:10:09] facilitating the growth of their brains, which was the most notable change between the hominins

[00:10:15] tribe that lived more than roughly one million years ago in the prior hominins tribe.

[00:10:20] Based on discovered skulls, scientists learned that the brain capacity of the genus Homo nearly

[00:10:26] doubled throughout the entire ice age. A huge brain can help us think, remember, and perform

[00:10:32] difficult cognitive tasks. So why hadn't the brain of prior humans evolved as such?

[00:10:38] The answer has something to do with energy. For most species, larger brain means enormous

[00:10:44] energy consumption. The ancient hominins were continually in a state of food scarcity.

[00:10:49] It was not until the hunter gather a period that they had the opportunity to store energy

[00:10:55] that allowed their brains to evolve. Although many of us are now troubled by body fat and struggle

[00:11:01] with managing our weight, our ancestors continuously suffered from fat deficiency and low body weight.

[00:11:08] Hence, at some point, fat storage evolved as a critical adaptive change in the human body.

[00:11:13] Without the body's ability and predisposition to store fat, perhaps the hominins would have never

[00:11:19] developed larger brains, and there would be no subsequent civilization.

[00:11:24] By the end of the ice age, all close relatives of humans became extinct,

[00:11:28] such as Homo-Hydlbergensis and Homo Neanderthals. Modern humans or Homo sapiens are the only surviving

[00:11:35] species within the genus. Why is this so? What makes us unique is the only surviving species of

[00:11:42] genus Homo? It's about time we mentioned the fifth stage of evolution. As mentioned earlier,

[00:11:49] the only surviving human species at this stage was the Homo sapiens. The fifth stage of evolution

[00:11:55] was primarily the formation of language and culture. Due to a special brain structure,

[00:12:01] humans possess special abilities, such as the ability to think and imagine. These abilities

[00:12:07] helped our ancestors to effectively communicate and be creative.

[00:12:12] Based on ruins in Africa, scientists estimated that Homo sapiens began long distance

[00:12:17] trading around 70,000 years ago, which means that there were already complex and massive social

[00:12:23] networks at the time. They were also able to make new tools, such as small stone points used

[00:12:29] as arrowheads, harpoons used for fishing, alts, and needles to fabricate clothing and nets.

[00:12:36] They even began to make some art objects, such as frescoes and carved figurines,

[00:12:41] stained necklace beads and so forth. Humans in the fifth stage of evolution started

[00:12:47] learning to express their beliefs and emotions, and there were dramatic changes in their ways

[00:12:52] of thinking and behavior. Compared with their ancient cousins, Homo sapiens shows more remarkable

[00:12:58] creative and communication skills. Homo sapiens is a species with a rich culture. Though culture

[00:13:05] itself is not a biological property, human cultural behavior with the abilities to utilize and change

[00:13:11] culture is a result of physiological adaptations present in modern humans. Such adaptation generates

[00:13:18] a strong impetus that speeds up the evolution of humanity. Lieberman believes that it is the

[00:13:24] best answer as to why Homo sapiens are the only extin human species. That concludes our content

[00:13:30] for part one. Let's do a brief review. There are five stages of human evolution that led to the

[00:13:37] present-day humans. The human body evolved into its current form by constantly adapting to

[00:13:42] environmental changes. To adapt to the shrinking rainforests and changes in living conditions,

[00:13:48] our A-Plyc ancestors learned to walk upright. To cope with the food shortages, they evolved thick

[00:13:54] molars. To deal with the continuous changes in habitat, they changed their foraging habits and

[00:14:00] turned to hunting and gathering. They developed the ability to walk and run long distances,

[00:14:06] as well as organs to maintain a lower body temperature. As food shortage became a thing of the past

[00:14:12] and they were able to store energy, their brain volumes began to grow larger. They became smarter

[00:14:18] and eventually, they also developed cultures and the ability to communicate using languages.

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