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Sagan goes on to extend the comparison in terms of surface area, explaining that if the Cosmic Calendar were scaled to the size of a football field, then "all of human history would occupy an area the size of [his] hand". [3] A similar analogy used to visualize the geologic time scale and the history of life on Earth is the Geologic Calendar.
As a result, each month now represents 1 of 12 billion years of the Earth's life. According to this calendar, the first life appears in January, and the first animals first appeared in May, with the present day taking place on May 18. Even though the Sun won't destroy Earth until December 31, all animals will die out by the end of May.
The last common ancestor between humans and other apes possibly had a similar method of locomotion. 12-8 Ma The clade currently represented by humans and the genus Pan (chimpanzees and bonobos) splits from the ancestors of the gorillas between c. 12 to 8 Ma. [31] 8-6 Ma Sahelanthropus tchadensis
Anatomically modern humans appear in Africa. [103] [104] [105] Around 50 ka they start colonising the other continents, replacing Neanderthals in Europe and other hominins in Asia. 70 ka Genetic bottleneck in humans (Toba catastrophe theory). 40 ka Last giant monitor lizards (Varanus priscus) die out. 35-25 ka Extinction of Neanderthals.
Visual representation of the Logarithmic timeline in the scale of the universe. This timeline shows the whole history of the universe, the Earth, and mankind in one table. . Each row is defined in years ago, that is, years before the present date, with the earliest times at the top of the ch
Human embryology is the study of this development during the first eight weeks after fertilization. The normal period of gestation (pregnancy) is about nine months or 40 weeks. The germinal stage refers to the time from fertilization through the development of the early embryo until implantation is completed in the uterus.
The oldest human skeletal remains are the 40ky old Lake Mungo remains in New South Wales, but human ornaments discovered at Devil's Lair in Western Australia have been dated to 48 kya and artifacts at Madjedbebe in Northern Territory are dated to at least 50 kya, and to 62.1 ± 2.9 ka in one 2017 study. [26] [27] [28] [29]
The smaller birth canal became a limiting factor to brain size increases in early humans and prompted a shorter gestation period leading to the relative immaturity of human offspring, who are unable to walk much before 12 months and have greater neoteny, compared to other primates, who are mobile at a much earlier age. [124]