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It orchestrates seasonal growth, development, reproduction, migration, and dormancy that affect survivorship and reproductive success. [14] Changes in photoperiod over days and seasons created the opportunity for the development of internal clocks and eventually create circadian and circannual rhythms. [3]
The March of Progress, [1] [2] [3] originally titled The Road to Homo Sapiens, is an illustration that presents 25 million years of human evolution. It was created for the Early Man volume of the Life Nature Library , published in 1965, and drawn by the artist Rudolph Zallinger .
Prehistory – Period between the appearance of Homo ("humans"; first stone tools c. three million years ago) and the invention of writing systems (for the Ancient Near East: c. five thousand years ago). Paleolithic – the earliest period of the Stone Age Lower Paleolithic – time of archaic human species, predates Homo sapiens
The stages are delineated through the development of structures, not by size or the number of days of development, and so the chronology can vary between species, and to a certain extent between embryos. In the human being, only the first 60 days of development are covered; at that point, the term embryo is usually replaced with the term fetus.
Photoperiod is the change of day length around the seasons. The rotation of the earth around its axis produces 24 hour changes in light (day) and dark (night) cycles on earth. The length of the light and dark in each phase varies across the seasons due to the tilt of the earth around its axis.
In regard to changes of ploidy, there are three types of cycles: haplontic life cycle — the haploid stage is multicellular and the diploid stage is a single cell, meiosis is "zygotic". diplontic life cycle — the diploid stage is multicellular and haploid gametes are formed, meiosis is "gametic".
All organisms follow a specific sequence in their development, [9] beginning with gestation and ending with death, which is known as the life cycle. Events in between usually include birth, childhood, maturation, reproduction, and senescence, and together these comprise the life history strategy of that organism.
160,000 years ago, Homo sapiens idaltu in the Awash River Valley (near present-day Herto village, Ethiopia) practiced excarnation. [59] 130–80 ka Marine Isotope Stage 5 . Modern human presence in Southern Africa and West Africa. [60] Appearance of mitochondrial haplogroup (mt-haplogroup) L2. 80–50 ka MIS 4, beginning of the Upper Paleolithic.