In biology , humans are usually studied as one of a variety of species on Earth . Learning human biology is sometimes also extended to the psychological aspect as well ragawinya , but usually not to the spiritual or religious . Biologically , humans are defined as darispesies hominid Homo sapiens . The only remaining subspecies of Homo sapiens is Homo sapiens sapiens . They are usually considered to be the only species that can survive in the genus Homo . Humans use bipedalnya locomotion ( two feet ) is perfect . With the second leg to move the body , two front legs can be used to manipulate objects using jarijempol ( thumb) . Average American adult female height is 162 cm ( 64 inches ) and an average weight of 62 kg ( 137 pounds ) . Men are generally larger : 175 cm ( 69 inches ) and 78 kilograms ( 172 pounds ) . Of course that is only an average figure , human physical form varies , depending on the place and historical factors . Although body size is generally influenced by heredity, environment and cultural factors also can influence it , such as human gizimakanan.Anak born after nine months in gestation , weighing in general 3-4 kilograms ( 6-9 pounds ) and 50-60 centimeters ( 20 -24 inches ) in height . Helpless at birth , they continue to grow for some years , typically reaching sexual maturity at around the age of 12-15 years . Boys will still continue to grow for several years after this , the growth usually stops at the age of about 18 tahun.Sebuah manusia.Warna framework of human skin varies from nearly black to reddish white . In general , people with ancestors from areas that have blistering skin blacker than people who descend from the area that has received little sunlight . ( However , this is of course not an absolute benchmark , there are people who have ancestors who came from areas less scorching and blistering , and these people may have different skin color in the spectrum.) On average , women have a little skin brighter than pria.Perkiraan human longevity at birth is approaching 80 years in affluent countries , this can be achieved thanks to the help of science and technology . Number of centenarians to the top in the world estimated at [ 1 ] about 50,000 in 2003 . Calculated maximum human life span is about 120 tahun.Sementara many other species are extinct , Man may still exist and thrive until now . Their success is due to the high intellectual power , but they also have disabilities . Humans tend to suffer from obesity more than other primates . This is largely because humans are capable of producing more body fat than their primate relatives . Because humans are bipedal alone ( only reasonable use two legs to walk ) , hip and spine areas also tend to be brittle , causing difficulty in moving the elderly . Also , human suffering women of childbearing relative complexity ( pain due to give birth to up to 24 hours is not common ) . Before the 20th century , childbirth was dangerous ordeal for some women , and is still happening in some remote locations or areas that are not growing in the world today.