What makes humans unique amongst the hominids

This evidence of interbreeding between groups that palaeontologists call separate species raises two crucial questions. First, given that most of us learned at school that species don't interbreed, should we change the definition we use for a species? Or should we remove the taxonomic separations erected purely from the morphology of fossils, and sink H. And second, how does the evidence of interbreeding affect our concept of modern humans, when the genomes of people today apparently contain differing levels of archaic genes?

In my view, the evidence that H. Doing so would produce a species that had a range of morphological variation several times that found in humans today, or in other existing primate species. These human lineages were distinct enough to build up well-differentiated genotypes and phenotypes although we know little of the Denisovan phenotype so far — even the inner ear bones of a Neanderthal are readily distinguishable from those of a modern human.

Furthermore, many closely related species of primates undergo limited interbreeding, including among our close ape and monkey relatives 7. So, for pragmatic reasons, I would retain these species categories while recognizing that this does not imply complete reproductive isolation 3. It is not yet clear whether the archaic DNA many of us carry is tied to any visible traits. Are some of the regional physical differences that I argue have largely evolved in the past 60, years within dispersing modern humans instead the result of Neanderthal or Denisovan genes?

Europeans do not seem to have inherited lighter pigmentation or cold adaptation from their Neanderthal predecessors, but what about their large noses or immune systems 8? What about the distinctive teeth and malarial resistance of some Australasians — could these be signs of a Denisovan heritage? More controversially, some of the known differences in coding DNA between Neanderthals and recent humans are associated with brain development and function 4.

Although the archaeological record of Africa suggests that it was the centre of origin for many innovations in modern human behaviour such as complex tools, symbolism and marine exploitation, some have argued that it was only on leaving Africa that modern humans ratcheted up their cognitive skills in response to the environmental challenges of Eurasia 9.

Now, instead, researchers may start to examine the possible phenotypic expression of Neanderthal, Denisovan or African archaic genes for cognition and intelligence. Terms such as 'archaic' and 'primitive' may be considered objective when used by palaeontologists, but they can be pejorative in common parlance.

If researchers want to continue the progress recently made in studying the origins of modern human variation, they will need to think long and hard about their aims, and the lexicon they use. One thing should be reiterated: all living humans are members of the extant species H.

It is important that we examine all the factors that lie behind our evolution, including the possible effects of interbreeding on the physiology of modern humans, but we will have learnt nothing in the past 50 years if we let small segments of distinct DNA govern the way we regard regional variation today.

Day, M. L'Anthropologie 95 , — Google Scholar. Wolpoff, M. Anthropos Brno 23 , 41—53 Stringer, C. Green, R. Science , — Reich, D. Nature , — Hammer, M. Natl Acad. USA , — Jolly C. Article Google Scholar. Abi-Rached, L. 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.

Human evolution took place as new genetic variations in early ancestor populations favored new abilities to adapt to environmental change and so altered the human way of life. Rick Potts provides a video short introduction to some of the evidence for human evolution, in the form of fossils and artifacts.

Skip to main content. Full Image. Human evolution Human evolution is the lengthy process of change by which people originated from apelike ancestors. Paleoanthropology Paleoanthropology is the scientific study of human evolution. The process of evolution 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.

Evidence of Human Evolution. Chickens, chimpanzees, and you - what do they have in common? Grandparents are unique to humans How strong are we? Modern H. Think of that, over a billion years and hardly any significant genetic change in that trait. But why speculate? An international team of 38 scientists led by Nenad Sestan of Yale University published a magnificent accomplishment in the quest to understand what makes the human brain unique. The investigators focused on 16 regions of the brains of adult humans, chimpanzees ape , and macaques monkey involved in higher-order cognition and behavior.

They looked at the genetic information in the cells of these regions by sequencing the total mRNA of each cell. Then they went further. They did this so they could get an integrated picture of every cell in a tissue, including its genetic and protein content. In addition to all kinds of variations in the molecular and cellular features between humans and chimpanzees, there was one finding that takes your breath away. They found some rare cells that are present in humans and are completely absent in chimpanzees and macaques.

These human-specific cells are located in the striatum , a nucleus an agglomeration of neurons in the midbrain. The name, striatum, comes from its appearance as stripes of gray and white matter.

Some cells in the striatum are activated by the neurotransmitter dopamine. They are known as dopamine interneurons.

Functionally, the dopaminergic dopamine-responsive striatum cells coordinate multiple aspects of cognition, including motor- and action-planning decision -making , motivation , reinforcement which carried to an extreme can end up in addiction , and reward perception. The newly discovered human-specific cells called dopamine interneurons were found to secrete dopamine.

And, these interneurons, in turn, activate the dopamine responsive neurons. Could it be that this is the location in the brain that makes us exceptionally, well…human? We simply do not know yet. Anatomically, we are the only mammals that have this specific dopaminergic cell type.

And we are apparently the only animal that engages in long-term planning. Varki is trying to uncover the mystery of human uniqueness. Now, if you guessed that Dr. These are the usual suspects in this field. But in actual fact, he is a glycobiologist. Glycobiology is the study of sugars in biology. Until quite recently, this field was the backwater of biochemical research.

And why not? DNA could crow about its function in storing all our genetic information. RNA could claim to be the crucial bridge between the information stored in DNA and the formation of proteins. And proteins had bragging rights as the machinery of life, performing all the functions that are critical for any living organism. But sugars? These molecules can be solitary or monosaccharides , such as glucose or fructose, or can form chains called polysaccharides.

But they are totally unglamorous. Glucose provides energy to the cell. Polysaccharides mainly cover the cell surface. They are basically dumb molecules. They have none of the sophisticated functions of information storage or enzymatic activity.

N-acetylneuraminic acid top and N-glycolylneuraminic acid bottom. What kind of polysaccharides cover the cell surface? In humans, the most common is a type of sialic acid called N-acetylneuraminic acid or Neu5Ac. Varki discovered that we are the only animal that has this molecule exclusively. All other animals have a different sialic acid on their cell surface, called N-glycolylneuraminic acid or Neu5Gc.