Future Human Speciation

future-human-evolution-speciationSpeciation is the process by which a new species is formed from a single initial species. There are a number of theories that might explain the phenomenon. For the astute visitor to our site, the rapid changes soon to be made possible in the human genome through the application of genetic engineering, combined with the geographical separation afforded by space colonization makes for an easy extrapolation of the process to humans.

George Lucas unwittingly had it right at the cantina in Star Wars. What he missed was the fact that all of the species gathered there at the watering hole were all from a common lineage; humans on earth having spread millennia ago, separated by distance, and subject to both direct germ-line manipulation and the environmental forces of the local planetary (or system) conditions.

Visit our Future Visions section for a look at some theoretical future human species.

Below we look at a few of the theories of how speciation occurs.

Speciation Theories

In order for speciation to occur, the following events must happen:

  1. There is a single species, made up of a set of interbreeding organisms.
  2. A genetic variant must spread through part of the species and the bearers of this variant must mate only with other bearers of the same variant.
  3. The species will have now split into two: from one initial population, two separate interbreeding populations will have evolved. Along the way, further phenetic, behavioral and ecological differences may also evolve.

Speciation comes about when there is recombination and isolation between different groups of genes, so that no longer can genes in one group be recombined with genes in another group. Once this occurs there is selection within each group of genes to interact well with the members of their own gene pool but there is no selection for them to be particularly functional with members of the alternate gene pool.

The crucial event, for the origin of a new species, is reproductive isolation.

Biologists need to understand how a barrier to interbreeding can evolve between the new species and its ancestors. There are three main theories as to how this can happen:

  • Allopatric speciation in which the new species evolves in geographic isolation from its ancestor.
  • Parapatric speciation: the new species evolves in a geographically contiguous pair of populations.
  • Sympatric speciation: the new species evolves within the geographic range of its ancestor.

Allopatric speciation

Allopatric speciation occurs when a new species evolves in geographic isolation from its ancestor. It can happen like this:

One species could split into two if a physical barrier, such as a new river, divided its geographic range. If the barrier is large enough, gene flow between them would cease and the two separate populations would evolve independently. Over time, different alleles would be fixed in them, either because of the hazards of mutation and drift, or because selection favored different characters in the two.

If the two populations are separated long enough for significant divergence to have taken place, then if the barrier is removed and the populations reunited, they might remain distinct from each other. A prezygotic or postzygotic isolation mechanism would prevent them from interbreeding. There would now be two species where there was formerly one.

A single randomly mating species is widely distributed through a geographical region.

Quite suddenly, a natural barrier forms, dividing the species into two separate groups.

Over the succeeding generations, either through selection or random events, the two populations come to differ.

When the barrier is removed, the populations are now so different that there is no reproduction between them: they have become two distinct species.

Peripheral isolation: a form of allopatric speciation.

There is a form of allopatric speciation called peripheral isolation or peripatric speciation.

In peripatric speciation a small population, at the extreme edge of the species’ range, is separated off. The same sequence of divergence and possible meeting of the two populations could then take place as in speciation by subdivision.

It has been argued that peripatric speciation has been much commoner than standard allopatric speciation. There are two reasons for this:

It may be physically more probable that a small population would be isolated at the edge of a species range than that a barrier would divide the whole of a species range.

It is thought to be common for isolated populations at the edge of a species range to be distinct in form, whereas the individuals in the main part of the species range show less variation. For example, the kingfishers on the peripheral islands have diverged more than would be predicted from the degree of variation on New Guinea.

There are two possible explanations for this divergence:

  1. Local adaptation: the conditions on the island may be such that natural selection favors a distinct phenotype there.
  2. Isolation: gene flow from the rest of the species may be reduced on the island, allowing the population there to diverge.

Whatever its explanation, if peripherally isolated populations are likely to diverge from the form of their ancestors, they may well be a common stage on the way to speciation.

Peripheral speciation may produce interesting features

Peripherally isolated populations are likely to be small, perhaps living in relatively extreme conditions and possibly having a non-representative sample of the ancestral species’s genes. Because of this, controversial conjectures have been made about how speciation works via peripherally isolated populations:

The speciating population may evolve rapidly (because the population is small) and by drift as well as selection.

The founder effect: the peripheral population is formed by a small number of founder individuals, who lack some of their ancestor’s genes. This is a controversial idea, because it implies that speciation might be non-adaptive.

Speciation might be accompanied by a genetic revolution: an extensive re-organization of the gene pool, which takes place in the extraordinary genetic and environmental conditions of the peripherally isolated population.

Parapatric speciation

In parapatric speciation, the new species evolve from contiguous populations.

Parapatric speciation occurs as follows:

Suppose that a population initially existed in an area to which it was well adapted, and that it then started to expand into a contiguous area in which the environment favored a different form. If the transition between the two environments was sudden, a stepped cline would evolve at the border.

As selection worked on the population in the new area, different genes would accumulate in it and the two populations would diverge to become adapted to their respective environments. If they diverged almost to be different species, the border would be recognized as a hybrid zone. The two populations would have separated while they were geographically contiguous, along an environmental gradient.

In contrast to the allopatric theory of speciation, the two populations on either side of the hybrid zone have diverged without any period of geographic separation.

Sympatric speciation

Sympatric speciation describes the splitting into two of a species without any separation of the ancestral species’ geographic range. Apart from hybrid speciation, which will be discussed later, it has been a source of recurrent controversy whether sympatric speciation ever happens.

Sympatric speciation could occurs as follows:

Imagine a bird species in which beak size determines the type of food the bird can eat. If the food is seeds, then there will be some distribution of seed sizes in the environment. Suppose also that there are several genotypes influencing beak size in the bird population. The fitnesses of the genotypes will be negatively frequency-dependent because as there are more birds with a certain size of beak they will compete with each other for food and lower one another’s fitness. There will be a stable polymorphism of beak genotypes.

Provided the seed sizes have a flat distribution as in the figure, the different genotypes will not have equal fitness. Birds with extreme beak sizes will experience less competition for food, and have higher fitness. In this circumstance, selection will favor assortative mating (tendency of like to mate with like) for beak size. Birds at the edge of the distribution by mating assortatively would produce more offspring like themselves, and therefore with higher fitness, than if they mated at random. As selection fixes assortative mating, the population will split into two new species: one with long beaks, the other with short.

The general conditions for sympatric speciation are therefore that the genotypes are adapted to different resources and the limited resources generate frequency-dependent selection. Then if the resources are not in the frequencies of the genotypes generated by random mating, sympatric speciation becomes a possibility.

Hybrid speciation

There is one type of sympatric speciation which is uncontroversial and well known to exist: hybrid speciation which regularly occurs in plants.

Interspecies hybrids are usually sterile because the chromosome pairs, which consist of one chromosome from one species and another chromosome from the second species, do not segregate regularly at meiosis.

When a hybrid species evolves, this sterility can be overcome by polyploidy: the chromosome numbers are doubled. Each chromosome pair at meiosis contains two chromosomes from one species, and regular segregation is restored. Polyploidization is encouraged by applying the chemical colchicine in the commercial production of new species. Many popular species of garden flowers such as these tulips (opposite) have been created like this. Hybrid speciation can also occur naturally at a low rate. In this case, a new hybrid species may evolve. Some hybrid species also evolve without polyploidy; the initial sterility of the hybrid is overcome by some other genetic means.

Polyploid hybrids are interfertile among themselves, but reproductively isolated (by the mismatch in chromosome numbers) from the parental species; they are therefore well defined new species.

Two problems likely to arise in the transition from a rare new hybrid genotype to a full hybrid species:

1. Finding a mate.

When a fertile polyploid hybrid first arises, it is one hybrid (or perhaps one of a small number) within two large populations of the parental species. The hybrid can only mate with other hybrids like itself and so natural selection on the hybrid therefore has a kind of positive frequency dependence: when it is rare its fitness is lower because of the difficulty of finding a mate.

This helps explain why hybrid speciation has been much commoner in some groups of plants than others. It is much easier for a new hybrid to cross the difficult transition stage, in which it is rare, if it has alternative reproductive options besides sexual cross-fertilization. It has been shown that hybrid speciation is commoner in groups in which asexual reproduction or self-fertilization are possible.

2. Ecological competition.

Two species with identical ecological needs will usually not be able to coexist; if one of the species can survive on a lower level of resources, it will drive the other extinct. When the hybrid arises, it will be in the same place as the parental species, and it is likely to have ecological needs that overlap with them. It is therefore thought that the hybrid species that have become established are those that happened to be adapted to different ecological niches from the parental species.

Those that were ecologically too similar to the parental species would have been lost. The survival of Iris nelsonii (pictured opposite in its swamp land habitat) may have been helped by the way it lives in habitats in between the other three species.

Reinforcement

Reinforcement is the process by which natural selection increases reproductive isolation.

Reinforcement can occur as follows:

When two populations which have been kept apart, come back into contact, the reproductive isolation between them might be complete or incomplete. If it is complete, speciation has occurred. If it is incomplete, hybrids would be produced. If the hybrids had lower fitness than either parental form, selection would act to increase the reproductive isolation because each form would do better not to mate with the other and form the disadvantageous hybrids. Speciation might then be speeded up by favoring genes which caused individuals to avoid mating with hybrids.

Reinforcement is a necessary requirement for both the parapatric and sympatric theories of speciation. It is the process by which a hybrid zone (an area of contact between different forms of a species) develops into a full species barrier.

Secondary reinforcement

Reinforcement is known as secondary reinforcement if the reproductive isolation has partly evolved allopatrically, and is then reinforced when the two populations come into secondary contact. Reinforcement could occur whenever two forms coexist, and the hybrids between them have lower fitness than crosses within each form.

Reinforcement can be simulated by artificial selection experiments. By continually selecting for assortative mating (the tendency of like to mate with like), it has been possible to obtain significant changes in prezygotic isolation mechanisms. However, the theoretical conditions for speciation to take place by reinforcement are difficult and it is controversial whether the process takes place in nature.

Gene flow

There is also the factor of gene flow. Selection might reinforce any isolation between the populations but, until isolation is complete, gene flow will be acting to equalize their gene frequencies. Once the two populations become genetically the same, there can no longer be selection to decrease breeding between them. Selection for reinforcement is likely to be strongest immediately after the two populations meet. If the necessary genetic variation in mating preferences is present, and selection is strong enough, the two species may completely split; but a gradual slide back into a single species is possible.

Allopatric speciation does not need a theory of reinforcement

A theory of speciation can avoid theoretical difficulties if it does not depend on reinforcement. The allopatric theory has this virtue. In the allopatric theory, it could be that reproductive isolation only ever evolves in allopatry (and when it does not the two populations simply collapse back into one when they meet); alternatively, it could be that partial reproductive isolation sometimes evolves allopatrically and is then reinforced on secondary contact. Either possibility fits in with the general theory of allopatric speciation.

The two alternatives – parapatric and sympatric speciation – require the theory of reinforcement: if reinforcement does not operate, neither do they.

Chromosomal evolution

It has been suggested that chromosomal evolution is exceptionally important in speciation. The theory runs like this:

Consider two forms of a chromosome, differing in an inversion. We can call the standard and inverted forms A and A’ . Suppose that A and A’ have identical sets of genes and produce the same phenotype, as in figure A. The two kinds of homozygote (AA and A’A’ ) will have identical fitness. The heterozygote is likely to be selected against, because recombinants between the two forms may have double sets of some genes, and lack others. We have here a precondition for the evolution of assortative mating. AA types should preferentially mate with otherAA types and avoid crossing with A’A’ ; and vice versa. A gene causing its bearer to mate assortatively with respect to chromosomal genotype will be favored. If assortative mating becomes established, speciation will result.

Applying the theory

If the theory is correct, we can predict an association between whether or not the members of a taxonomic group have an inbred population structure, their rate of speciation, and of chromosomal change.

Some species live in small social groups, or otherwise have subdivided populations, and in these the degree of inbreeding will be higher than in a species in which individuals outbreed in a large population. Bush et al. tested whether genera whose members live in small family groups have a higher rate of speciation and chromosomal evolution than panmictic genera.

They collected evidence for 225 vertebrate genera. For each, they counted the number of species in it and its chromosomal diversity. The two are correlated, as would be predicted by almost any theory. They then argued that the taxa with higher speciation rates tended to have subdivided population structures; mammals, especially primates and horses (though not whales), have high rates of speciation and chromosomal evolution; amphibians, reptiles, and fish have lower rates – which perhaps explains the existence of living fossils. Primates (like these chimps pictured opposite) and horses are two taxa that usually live in social groups.

It is therefore possible that taxa with subdivided population structures do have higher speciation rates, and maybe this is due to the way chromosomal evolution can proceed more rapidly in these kinds of species.

Speciation – Summary

The evolution of a new species happens when one population of interbreeding organisms splits into two separately breeding populations.

It has been a matter of controversy whether new species evolve only from sub-populations that are geographically isolated (allopatric) from the ancestral population, or whether they can also evolve from sub-populations that are contiguous with (parapatric), or overlap (sympatric), the ancestral population.

Allopatric speciation may be by subdivision of the species range or by a peripheral isolate – a small population which becomes cut off at the edge of the species range.

Parapatric speciation could happen if a steep cline evolved into a hybrid zone and barriers to interbreeding then evolved.

Sympatric speciation is most likely if selection first establishes a stable polymorphism and then favors assortative mating within each polymorphic type.

Many new plant species have originated by hybridization of two existing species, followed by polyploidy of the hybrids.

Reinforcement is the enhancement of reproductive isolation by natural selection: forms are selected to mate with their own, and not with the other, type. Sympatric speciation requires reinforcement to happen; parapatric speciation usually requires it; allopatric speciation can take place with or without reinforcement.

 

Intelligent Design

intelligent-design-on-the-future-human-evolution-websiteWhat in the world happened to Intelligent Design?

Much to my chagrin, I revisit Intelligent Design years after the writing of my original article where I merely put forth the premise of ID.  That is, believers (some scientists along with the religious right) purport that the universe, and life itself, is too complex and specific to have happened purely by chance.  The ID theory proponents generally agree that fossil and other evolutionary evidence is genuine and point toward the progressive development of higher forms of life.  Where they diverge is that rather than believing random chance at the helm, ID theory proponents suggest, much like the Deist beliefs of the American founding fathers, that a creator put rules in place for the unfolding of life as well as the deployment of the laws of physics.

I will admit, I was rather pleased that a sort of compromise had been reached. Since we have yet to to come up with any plausible explanation of how the universe got here in the first place, ID sounded like it had as much credibility on that count as “quantum fluctuation”.  Where’d the quantum come from to fluctuate? Two theories in peaceful coexistence.

So silly me turned my attention to other things. Things one can actually do something about, like the FUTURE.

Long story short, I am making my rounds on the website, updating this, deleting that, adding new, etc. and I come across my old harbinger of peace, ID.  A few Google searches in and I start seeing things like conspiracies, court battles, law suits, and as much polarization and hostility as one ever saw in the original evolution vs. creation debate.

This evening I’ve spent as much time as I  am going to looking for a rational dialogue or even a forum for one. Theories abound.  I am having trouble seeing the harm in teaching ID as a theory. In fact, it might take some of the mysticism and superstitious hold some religions can exert on the unsuspecting (if you think I mean yours, I am sure you’re quite mistaken. Yours is completely different).

And before you think I’m picking exclusively on the dogmatists of the right handed variety, here ye, here ye, dogmatists of the highbrow sort who vehemently denounce even the slightest possibility of the “supernatural” which is merely a euphemism for the unexplained. Is it really necessary to be anti-religious?

For extremists everywhere a message for you In the words of Shakespeare:

Methinks Thou Dost Protest Too Much.

 

The Panspermia Theory

panspermia-and-the-future-of-human-evolution

Click for Larger Image

Panspermia, translated as “seeds everywhere,” is a theory that the seeds of life are spread throughout the universe in cosmic dust or perhaps in the tails of comets, and that life on Earth began when they managed to reach the surface of the planet. The theory has origins in the ideas of Anaxagoras, a Greek philosopher, but in modern times was revived by Sir Fred Hoyle, the famous British astronomer.

There is some evidence to suggest that bacteria, the probable mechanism, or panspermia “seed” may be able to survive for very long periods of time even in deep space. Two Cal Poly scientists demonstrated back in 1995 that bacteria can survive without any metabolism for at least 25 million years, making bacteria most likely immortal. Past studies out of India, further attesting to the robustness of life, have found bacteria more than 40 km up in Earth’s atmosphere where it would be unlikely to have come from our lower atmosphere.  Additionally bacteria Streptococcus mitus which was inadvertently carried to the moon on the 1967 Surveyor 3 spacecraft, was easily revived after being taken back to earth three years later.

One characteristic of panspermia would be that life in the universe would have a very similar biochemistry. So the high-altitude bacteria might be expected, whether of earth or extra-terrestrial origin, to appear very similar to terrestrial forms. This is not a testable hypothesis until life on another planet can be examined.

A major obstacle to the credibility of Panspermia theory is the fact that bacteria may not survive the tremendous heat and forces of an earth impact.  No studies or evidence have been conducted or collected to confirm or deny this likelihood.

Regarding known extraterrestrial material, the  “ALH84001″ rock sample believed to have come from Mars, shows some indication that microbial life may have been present at some point in the past. This widely disputed instance is the only indication we have of extraterrestrial life.

Some have taken the theory as an answer to those arguing the improbability of life spontaneously occurring on earth, that it happened elsewhere and traveled through the cosmos.

One of the newer wrinkles in the theory, purported by pranspermia.org, is that of Cosmic Ancestry.

Hoyle (and cohort Wickramasinghe) after reawakening the idea of panspermia, later broadened it to include a new understanding of evolution. They theorized that life could not have made the leaps and bounds from a single cell to humans in a mere 4 billion years; rather, the code of evolution was carried along with the seeds of life and indeed must always be so. Much in the same way the big bang set the rules for physics, life establishes the rules for its unfolding.

Parallel to their theorizing, and In the early 1970s, another man, British chemist and inventor James Lovelock proposed the theory that life controls Earth’s environment to make it suitable for itself. The theory, Gaia, as seen from a Darwinian perspective, looks suspiciously teleological. Nevertheless, the publishers of panspermia.org are calling the combination of Gaia with Hoyle and Wickramasinghe’s “strong” theory of panspermia, Cosmic Ancestry.  They say that  that life can only descend from life as equally evolved as itself. It also suggests that life can only come from life, requiring a supernatural being.

Now there’s a interesting combination of science, philosophy, and religion.

The straight panspermia theory has been popular in science fiction. Invasion of the Bodysnatchers by Jack Finney has been made into a feature film three times. In The Day of the Triffids, the first person narrator, writing in historical mode, takes care to reject the theory of panspermia in favor of the conclusion that Soviet biotechnology created carnivorous plants. It’s not hard to see why when you examine the fact that while interplanetary, interstellar, and perhaps even intergalactic “contamination” of life may be possible, there’s a lot of baggage associated with that simple scenario. Not the least of which is aimed at those who would use it it in lieu of spontaneous life occurring on earth as an escape mechanism. Cosmic Ancestry notwithstanding, life has to have started somewhere.  Magic fairy dust hardly concludes that creationism vs. evolution debate.

 

Human Evolution & Origins

You may have seen the following sentiment on other pages of this “Evolution & Origins” section in addition to other places:

It does not matter whether you believe we descended from monkeys and share a common genetic heritage with the first living cell on the planet, or whether that we are a unique Being breathed into life by an almighty god, or even if you subscribe to the theory that the Anunnaki created the Sumerians by mixing their own DNA with that of the most advanced Hominid they could find 6,000 years ago, the open book of the future lies ahead for us to write with our deliberate and thoughtful actions:  The Future of Human Evolution is ours to determine.

Therefore this section attempts to cover the major explanations of existence, evolution being explored further as the leading scientific theory. It makes no attempt to make converts from one’s belief system into another. It is, and we hope you will agree, really interesting to explore these various ideas.

Inside Human Evolution & Origins

What is Evolution?

In our opening article to the section, we bring you a discussion of what evolution is and how evolution works so that you can understand the principles and mechanisms behind it so you can journey with us as we extrapolate these concepts, along with an estimation of mankind’s proclivities, to where the future of human evolution may be headed.

Meet Your 10 Closest Evolutionary Relatives

Human evolution timeline, illustrations, and a few brief facts of Homo sapiens’ nearest hominid relatives. The most enlightening fact is how very brief our reign on earth has been.

Cretenists vs Evilutionists

Understanding the role and concepts of Micro-Evolution and Macro-Evolution against the backdrop of the creationist controversy and in relation to the mission of the site might be of interest to some visitors.

The Panspermia Theory

This theory suggests life originated extraterrestrially and may travel from place to place on cosmic dust. Recent developments have seen a supernatural rider attached to central theme.

 

Intelligent Design

Where did all the moderates go? This once compromise theory between religious fundamentalists and extreme scientific atheism has taken some hits. Is it down and out?

Meet our Top 10 Closest Evolutionary Relatives

Timelines, Images, and Descriptions of Human Ancestry

Hopefully you’ve read our article on the Evolutionary Process.  Also by now you hopefully know we’re all about the Future of Human Evolution regardless of whether your particular belief system allows you to consider the science around our past and evolutionary history, or not.

In this abbreviated count-down article we’ll relay some of science’s best conclusions based on fossil records and in a few cases, some DNA to bolster the conclusions.  Our goal in this article is not to convince anyone of anything, rather lay it out there for your perusal and I dare say, enjoyment.

Sometime science is just plain fun!


10. Sahelanthropus tchadensis

The Human Evolution Time Line - Sahelanthropus tchadensis

Sahelanthropus tchadensis Lived About 7 million years ago in West-Central Africa

Sahelanthropus tchadensis

  • Lived: About 7 million to 6 million years ago in West-Central Africa
  • Male/Female sizes unknown

Not discovered until 2001, our earliest known human relative Sahelanthropus tchadensis, displayed both ape and human features. Only cranial fossils have been found so far in modern-day Chad. This species had small canine teeth and walked upright on two legs instead of four—two characteristics that separate us from apes and allow scientists to count them among our ancestors.

09. Ardipithecus ramidus

The Human Evolution Time Line - Ardipithecus ramidus

Ardipithecus ramidus Lived 4.4 million years ago in Eastern Africa - Average female 3-11 110 pounds

Ardipithecus ramidus

  • Lived 4.4 million years ago in Eastern Africa
  • Average male: size unknown
  • Average female: 3-11, 110 pounds

Was Ardipithecus ramidus really an eight-year-old modern boy? Scientists suspect this early human ancestor both ran around chasing animals (bipedal) and climbed trees. Ar. ramidus fossils show a divergent larger toe and a rigid foot—evidence of walking on two legs. But pelvis reconstructions suggest it had adaptations for both tree-climbing and bipedalism. Ar. ramidus had teeth suitable for a diet of plants, meat, and fruit but probably not sturdy enough to crack nuts.

08. Australopithecus afarensis

The Human Evolution Time Line - Australopithecus afarensis

Australopithecus afarensis - Lived Between 3.85 million and 2.95 million years ago in Eastern Africa

Australopithecus afarensis

  • Lived between 3.85 million and 2.95 million years ago in Eastern Africa
  • Average male: 4’11”, 92 pounds
  • Average female: 3’5”, 62 pounds

Lucy, the world-famous Australopithecus and her cohorts lived across East Africa for nearly 900,000 years—neary five times as long as modern humans have been on the planet. They walked on two legs, had flat noses, and prominent jaw bones. Similar to chimpanzees today, they had childhoods and adolescent periods that were brief compared with those of modern humans.

07. Australopithecus africanus

The Human Evolution Time Line - Australopithecus africanus

Australopithecus_africanus

Australopithecus africanus

  • Lived: Between 3.3 million and 2.1 million years ago in Southern Africa
  • Average male: 4’6”, 90 pounds
  • Average female: 3’9”, 66 pounds

Living amid numerous predators, Australopithecus africanus weren’t always at the top of the food chain, and they likely lived in groups for protection against predators. With a combination of human and ape features, they were anatomically similar to their cousins Au. afarensis. The first Au. africanus fossil to be discovered, in 1924, was known as the Taung child. Paleontologists have since realized that damage to the fossil’s skull indicates that the child was captured and eaten by a giant eagle. The fossil established that the earliest human ancestors lived in Africa.

06. Paranthropus boisei

The Human Evolution Time Line - Paranthropus boisei

Paranthropus boisei Lived Roughly 2.3 million to 1.2 million years ago in Eastern Africa

Paranthropus boisei

  • Lived Roughly 2.3 million to 1.2 million years ago in Eastern Africa
  • Average male: 4’6”, 108 pounds
  • Average female: 4’1”, 75 pounds

Paranthropus boisei are best known for their large cheek bones that housed powerful chewing muscles and big teeth. Fossils suggest they munched on both tough foods like nuts and roots and soft foods like fruit. They had the thickest tooth enamel of the early human ancestors.

05. Australopithecus sediba

 The Human Evolution Time Line - Australopithecus sediba

Australopithecus sediba

Australopithecus sediba

  • Lived: About 1.95 million and 1.78 million years ago in Southern Africa

Our most recently discovered relative is Australopithecus sediba. Its fossils have characteristics that start to resemble those of our Homo genus, as our ancestors inched further away from our ape cousins. Au. sediba likely walked in an increasingly human-like way and had facial features that more closely resembled you more than a chimpanzee, but they still had the small brains and long upper limbs found in our earlier tree-dwelling relatives.

04. Homo erectus

The Human Evolution Time Line - Homo erectus

Homo erectus

Homo erectus

  • Lived: 1.89 million to 143,000 years ago in Northern, Eastern, and Southern Africa; parts of East and West Asia; possibly Europe
  • Average male and female: 4’9” to 6’1”, 88-150 pounds

As possibly the longest-existing member of human family tree, Homo erectus lasted about nine times as long as modern humans have so far. Its fossils—spread out over at least two continents—are highly varied. Early fossils found in Africa show Homo erectus may be the first of our ancestors to have modern-day proportions: elongated legs and shorter arms relative by today’s standards to torso size. Thanks to better hip support that allowed them to walk long distances, they settled into new habitats spanning Africa and Asia. They made tools, including stone tools and those to butcher large animals, and cared for their old and weak members.

03. Homo heidelbergensis

The Human Evolution Time Line - Homo heidelbergensis

Homo heidelbergensis

Homo heidelbergensis

  • Lived: 700,000 to 200,000 years ago in Northern, Eastern, and Southern Africa; Europe
  • Average male: 5’9”, 136 pounds
  • Average female: 5’2”, 112 pounds

Homo heidelbergensis can boast of several firsts among human ancestors. They were the first to build simple shelters out of wood and rock and the first to regularly hunt large animals. They were among the first to inhabit cold European climates. The jury’s still out on other possible firsts, such as earliest control of fire and first use of wooden spears.

02. Homo neanderthalensis

The Human Evolution Time Line - Homo neanderthalensis

Homo neanderthalensis Lived About 200,000 to 28,000 years in Europe and Asia

Homo neanderthalensis

  • Lived: About 200,000 to 28,000 years in Europe and Asia
  • Average male: 5’5”, 143 pounds
  • Average female: 5’1”, 119 pounds

Our closest extinct relative, Neanderthals were possibly the first human ancestors to speak and bury their dead. They hunted large animals, ate plant foods, lived in shelters, wore clothing, and created symbolic or ornamental objects. Their broad bodies, short legs, and large noses, which could humidify and warm cold, dry air, allowed them to survive in cold climates. Some anthropologists have speculated that Neanderthals and modern humans likely got a little frisky with one another, but recent DNA test show no substantive proof of this.

01. Homo floresiensis

 The Human Evolution Time Line - Homo floresiensis

Homo floresiensis compared to modern human

Homo floresiensis compared to modern human

  • Lived: 95,000 to 17,000 years ago in Flores, Indonesia
  • Average male: unknown
  • Average female: 3’6”, 66 pounds

Homo floresiensis, appears to be the last of our hominin cousins to go extinct, even though they appeared after we Homo sapiens. Their fossils have been located on only a single Indonesian island indicating that in addition to their stature they may have shared a common pattern of genetic isolation as has the much more recent 2800 year old African Pigmy populous (the two are not genetically related any more than other Homo sapiens). They had large teeth, recessed chins, large feet relative to short legs, and brains roughly one-third the size of ours. Despite their small bodies and brains, they hunted and may have used fire. Their small stature likely helped them survive on an island with limited resources, and they may have been vulnerable to large predators such as Komodo dragons.

00. Homo sapiens

The Human Evolution Time Line - Homo sapiens

Homo sapiens female

Homo sapiens female

  • First appeared: About 200,000 years ago
  • Wide variety of heights, weights, and skin tones across the globe

Modern humans evolved in Africa during a period of climate change roughly 200,000 years ago and shared the planet with a few other human species. We bounced back from a period of near-extinction about 74,000 years ago—at our lowest point, our team amounted to about 10,000 reproducing adults—to introduce Earth to agriculture, animal domestication, neighboring planets, and a fascination with our extinct predecessors as well as the future of human evolution.


Here is a combined timeline so that you can see the relative lengths and positions of the various species across the 7 million year span.

Click for full-sized image.

Top 10 Evolutionary Human Ancestors Timeline by the Future Human Evolution Website

Top 10 Evolutionary Human Ancestors Timeline by the Future Human Evolution Website