Archeological evidence refers to the things earlier people made and the places where scientists find them. By studying this type of evidence, archeologists can understand how early humans made and used tools and lived in their environments.
The process of evolution involves a series of natural changes that cause species populations of different organisms to arise, adapt to the environment, and become extinct. All species or organisms have originated through the process of biological evolution. In animals that reproduce sexually, including humans, the term species refers to a group whose adult members regularly interbreed, resulting in fertile offspring -- that is, offspring themselves capable of reproducing. Scientists classify each species with a unique, two-part scientific name.
In this system, modern humans are classified as Homo sapiens. Evolution occurs when there is change in the genetic material -- the chemical molecule, DNA -- which is inherited from the parents, and especially in the proportions of different genes in a population. Genes represent the segments of DNA that provide the chemical code for producing proteins. Information contained in the DNA can change by a process known as mutation. The way particular genes are expressed — that is, how they influence the body or behavior of an organism -- can also change.
Evolution does not change any single individual. Instead, it changes the inherited means of growth and development that typify a population a group of individuals of the same species living in a particular habitat. Parents pass adaptive genetic changes to their offspring, and ultimately these changes become common throughout a population.
As a result, the offspring inherit those genetic characteristics that enhance their chances of survival and ability to give birth, which may work well until the environment changes. Over time, genetic change can alter a species' overall way of life, such as what it eats, how it grows, and where it can live. The eruption of a super volcano, Mount Toba, in Sumatra 70, years ago may have led to a 'nuclear winter', followed by a 1,year ice age.
This sort of event would have put immense pressure on humans. It may be that humans were only able to survive these extreme conditions through cooperating with each other.
This may have led to the formation of close family groups or tribes and the development of some of the modern human behaviours we are familiar with today, such as cooperation. Between 80, and 50, years ago another wave of humans migrated out of Africa. Due to their newly cooperative behaviour they were more successful at surviving and covered the whole world in a relatively short period of time.
As they migrated they would have encountered earlier, primitive humans, eventually replacing them. A map showing human migration out of Africa. Image credit: Genome Research Limited. Homo neanderthalis , or Neanderthals as they are more often known, are an extinct species of human that was widely distributed in ice-age Europe and Western Asia between , and 28, years ago.
They were characterised as having a receding forehead and prominent brow ridges. Since then, researchers have been striving to uncover the position of Homo neanderthalis in modern human evolution. Homo neanderthalis appeared in Europe about , years ago and spread into the Near East and Central Asia. They disappeared from the fossil record about 28, years ago.
Their disappearance has been put down to competition from modern humans, who expanded out of Africa at least , years ago ,year-old remains of modern humans have been found in Israel , suggesting that there would have been a period of co-existence. Did the two species interbreed? Have Neanderthal genes therefore contributed to the modern human genome? Initial studies of DNA from the mitochondria of Neanderthals showed that their mitochondrial DNA looks quite different to that of modern humans, suggesting that Homo neanderthalis and Homo sapiens did not interbreed.
They also identified another archaic human group called 'Denisovan', named after the Siberian cave in which the fossil finger, from which the DNA was obtained, was discovered. In they obtained a more refined Neanderthal genome sequence from a 50,year-old Neanderthal toe bone, found in the same cave in southern Siberia.
The genome sequence suggested that early modern non-African humans interbred with their now extinct ancient human cousins. DNA can survive in bone long after an animal dies. Over time the DNA from various microbes that encounter the skeleton will also invade the bone. Scientists therefore have to ensure that they sequence only the Neanderthal genome and get rid of any DNA material left behind by these microbes or resulting from contamination by modern humans who handle these bones.
They concluded that H. Several Homo species emerged following H. The best known one is Homo neanderthalensis Figure 3 , usually called Neanderthals and they were known as the European branch originating from two lineages that diverged around , years ago, with the second branch lineage Homo sapiens known as the African branch.
The first Neanderthal fossil, dated from around , years ago, was found in La Sima de los Huesos in Spain and is considered to originate from the common ancestor called Homo heidelbergensis [ 6 ]. Neanderthals used many of the natural resources in their environment: animals, plants, and minerals.
Homo neanderthalensis hunted terrestrial and marine ocean animals, requiring a variety of weapons. Tens of thousands of stone tools from Neanderthal sites are exhibited in many museums. Neanderthals created paintings in the La Pasiega cave in the South of Spain and decorated their bodies with jewels and colored paint. Graves were found, which meant they held burial ceremonies. Denisovans are a recent addition to the human tree. In , the first specimen was discovered in the Denisova cave in south-western Siberia.
Very little information is known on their behavior. They deserve further studies due to their interactions with Neandertals and other Homo species see below [ 7 ].
Fossils recently discovered in Morocco North Africa have added to the intense debate on the spread of H. The location of these fossils could mean that Homo sapiens had visited the whole of Africa.
In the same way, the scattering of fossils out of Africa indicated their migrations to various continents [ 9 ]. While intensely debated, hypotheses focus on either a single dispersal or multiple dispersals out of the African continent [ 10 , 11 ]. Nevertheless, even if the origin of the migration to Europe is still a matter of debate [ 12 ], it appears that H.
Therefore, it could be that migration to Europe was not directly from Africa but indirectly through a stay in Israel-Asia. They arrived about 45, years ago into Europe [ 14 ] where the Neanderthals were already present see above.
Studies of ancient DNA show that H. Several thousand years ago H. The quality of the paintings shows great artistic ability and intellectual development. Homo sapiens continued to prospect the Earth. They crossed the Bering Land Bridge, connecting Siberia and Alaska and moved south 12, years ago, to what is now called Chile. Homo sapiens gradually colonized our entire planet Figure 5. Neolithic Period means New Stone Age, due to the new stone technology that was developed during that time. The Neolithic Period started at the end of the glacial period 11, years ago.
There was a change in the way humans lived during the Neolithic Period. Ruins found in Mesopotamia tell us early humans lived in populated villages.
Due to the start of agriculture, most wandering hunter-gatherers became sedentary farmers. Instead of hunting dogs familiar with hunter-gatherers, farmers preferred sheepdogs [ 16 ]. In the Neolithic age, humans were farming and herding, keeping goats and sheep. By John Pickrell. Five skulls belonging to some ancestors and relatives of modern humans. From left to right, the skulls are: Australopithecus africanus Australopithecines appear. First human ancestors to live on the savannah.
Lucy, famous specimen of Australopithecus afarensis , lives near what is now Hadar, Ethiopia. Paranthropus, lives in woods and grasslands, has massive jaws for chewing on roots and vegetation. Becomes extinct 1. Homo habilis appears.
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