Evolution by natural selection needs time. Therefore, we will once more set the time frame in which evolution took place. The question, what was before the Big Bang and what is outside our universe, is something we may well leave to physicists. (They could claim that the question “what was before the Big Bang?” was futile, as before the Big Bang, time itself did not exist).

The Big Bang happened around 13.8 billion years ago and since then our universe expands. Our solar system with our planet earth came into being around 4.6 billion years ago. The first primitive life forms arose around 3 billion years ago in water. About half of the time that has passed since then, life on earth remained single-celled. Around 1.5 billion years ago, one single celled organism swallowed another one. However, it was not digested, but continued living symbiotically inside the organism that had taken it up and took over partial functions of the combined organism. Such eukaryote cells are the building blocks of multicellular organisms with the single cell in complex organisms not being autonomous anymore, but rather becoming more and more functionally specialized (organ cells).

Since then, diverse forms of multicellular life have developed. The 4 cm measuring Pikaia that lived 525 million years ago in water were the first representatives of the chordates known to us (we also belong to the animal phylum of chordates). Chordates have a rod in their back (the chorda) as a common feature. The chorda lies over the gut and under the neural tube. The first steps on land were undertaken by the first amphibiae around 300 million years ago. The age of the dinosaurs started around 235 million years ago, lasted for around 150 million years and ended 66 million years ago, when a comet hit the earth. The corresponding crater was discovered in the 1990s right next to the large Mexican peninsula Yucatan, and the diameter of the comet was estimated to around 10 km.

To give a feeling for evolutionary time frames, using a fictious day or a fictitious year is a popular approach, as these are time frames that are ascertainable to our senses. Table 1 displays some milestones of evolution in relation to a fictitious year.

Table 1: Milestones in the history of the earth in a fictitious year with the last day being broken down into hours, minutes and seconds

As a child I was very impressed by the French animated film “Once Upon a Time….Man”. In the German edition the intro theme was sung by the 2014 deceased musician and composer Udo Jürgens. This small piece of music left a strong not only content driven, but also emotional memory. The memory of the whisperingly sung “Was ist Zeit” (What is time) that follows the line “Tausend Jahre sind ein Tag” (Thousand years are a day) still raises goose bumbs on my skin. Therefore, I also want to use this massstab: If 1000 years correspond to one day, the dinosaurs would have gone extinct 66,000 days ago (66 million years), the last common ancestor of man and chimpanzee would have lived 6,000 days ago (6 million years) and Homo sapiens would not be roaming the earth for longer than just 300 days (300,000 years), most of which as hunter-gatherer. Only 12 days ago (12,000 years), the first Homo sapiens would have settled down for farming. The use of oil as a source of energy would have started 6 hours ago (250 years). Since 5 hours ago (1804) the world population would have reached 1 billion, since less than the length of a football match (around 1960) over 3 billion and since 13 minutes (2011), it would have surpassed 7 billion Homo sapiens.

The dawn of life

Mechanisms of selection certainly also play a role in astrophysics; however, we want to focus on the evolution of life. Richard Dawkins’ 1976-book “The Selfish Gene” can well be seen as a fundamental book of evolutionary theory (4).

Stable, self reproducing molecular structures

Precondition for the emergence of life was the formation of stable structures that can reproduce, which means they are able to produce more or less identical (or reciprocal) copies of themselves. If atoms converge again and again with stable interdependencies that lead to stable structures, the complex formations arising are called molecules. Stability over time can be reached by long-term persistance or by replication or reproduction, which is the repetitive emergence of a certain molecule type. In our world, the long persistence over time is rather found in inanimate matter. Persistance over time by emerging and wearing away is a basic principle of life. A type of living being is more persistent over time if it does not depend on the single individual being, but rather exists as a concept, which propagates by replication over time. On a molecular level, chemical reactions permanently take place, which make molecules emerge and wear away, however we would not call this life. Water molecules consist of oxygen and two hydrogen atoms. The water molecule (H₂O) is thus relatively simple build and could be seen as a manifestation of the affinity between oxygen and hydrogen, making water an omnipresent molecule on earth. An imbeded construction plan for water is not required for the formation of this molecule.

The underlying tendency of hydrocarbon compounds to form chains makes them the backbone of larger and more complex molecules, which are the domain of organic chemistry. These hydrocarbon molecules can take oxygen, nitrogen or phosphor atoms on board and form complex spatial structures with foldings and branchings. Most organic molecules do not need an imbedded construction plan neither, as they simply emerge by “trial and error” of random constellations and connections formed, some of which arise often and some rarely. Complex hydrocarbon compounds are taken up and metabolised by forms of life from bacteria to elephants. On earth, 4 billion years ago, no life existed, yet, so that atom- or molecule conglomerates could emerge and wear away undisturbed. Millions of identical molecules could emerge through atom-affinity and atom-frequency driven accumulation of certain combinations. Crystalline growth for example consists of multiple identical molecules attaching to each other. Crystalline structures are e.g. metals, sugars, salts and snow.

With growing complexity one can expect less and less that such complex structures arise randomly again and again with the same building blocks in the sam constellations. Not without an embedded plan.

On a molecular level, molecules must have arisen, which are able of replicating their own structure and doing so implement an embedded construction plan. Richard Dawkins in the “The selfish gene“ called such molecules with the embeded ability to replicate as “replicators”. Around 3-4 billion years ago, the construction blocks were floating in the broth around the replicator with certain affinities to other components of the replicators. Some affinities were stronger, so that especially copies of replicators with components that have high affinities to each other, arise. For implementing a construction plan, which is embedded in the replicator, reading mechanisms must exist that decode for example the order of molecule-components in the replicator into information that is relevant for forming the daughter molecule. For example, the order of molecules in the replicator must be decoded into the information for the formation of the replicate. In principle the information in the replicator could be used for building an identical molecule with identical building blocks in the identical order. If we, however, look at the shape of a single building block, it becomes clear that an identical copy would lack attachment sites to the original: Two balls can not entangle with each other in a stable way, but a ball lies stable in a bowl. Two keys do not form a stable connection, but a key sticks stable in a fitting keyhole. The principle that prevailed in life is therefore that of negative copies. The order of nonidentical molecule compounds of the negative copy molecule is defined by the order of the compounds of the positive original. From the positive a negative copy arises, from which a positive copy arises, from which a negative copy arises and so forth.

Such a posoitive-negative replication principle has preveailed in the genetic code of the desoxyribo- and ribo-nucleic acids (DNA and RNA): The order of 4 nucleic acids adenine (A), guanine (G), cytosine (C) and Uracil (U) are the 4 letteres of the RNA alphabet. DNA contains thymine (T) instead of U.

In DNA, the hydrogen-bound mediated positive-negative affinity in the genetic code consists between G-C and A-T (or C-G and T-A).

In RNA, the hydrogen-bound mediated positive-negative affinity in the genetic code consists between G-C and A-U (or C-G and U-A).

Thus, DNA and RNA had become data carriers on which the information of life is coded as genetic code. For the production of proteins an RNA copy is generated as a negative copy from the corresponding DNA, the so called messenger RNA (mRNA). This mRNA is being tailored by “splicing”, so that the protein-coding RNA only contains the information required for the protein to be synthesized. Thre RNA bases code for one amino acid and the order of base triplets on the RNA gives the order of amino acids of the protein (with three possible orders depending on the reading frame used). The actual protein synthesis is carried out by ribosoms which walk along the mRNA joining the amino acids, base-triple by base triplet.

How did complex forms of life develop over millions of years? According to common definitions of life found in biology books, one would not count self replicating molecules such as DNA as forms of life. Even viruses, that already show quite some complexities, are not considered to be life if I follow my biology schoolbook from the 1980s. If metabolism, reproduction and evolution are considered as “life-defining” criteria, viruses underly evolutionary mecanisms, but do not really have an own independent metabolism. For reproduction they depend on replicatory features of their host organism, e.g. for the replication of their RNA or DNA and for the synthesis of structural elements such as simple enzymes and structural proteins. But, if viruses rely on host organisms of higher complexity, the development of complex viruses relied on the development of complex (living?) host organisms, to pack the naked (future) virus genome into structures, that actually make a virus out of the naked genome. Viruses can emerge from complex organisms by release of endogenous viral genome sequences together with hijacked structural elements (5). Did viruses exist before living organisms or did viruses require living organisms from which to emerge? This apparent hen-egg problem can be overcome by abandoning the strictly binary distinction between living and not-living organisms. The virus does not care if its structures come from a living or a non-living being. (Certainly a virus lacks a will, thus a virus can not be able not to care. A virus can only be).

Bacteria count as living beings. When it comes to pure numbers (and masses), bacteria are even the dominant form of life on earth. In a human’s gut only, according to Ed Yongs book “I contain multitudes”, an estimated 100 Trillion (10¹⁴) bacteria live. Following this, my gut contained around a million more bacteria than there are stars in our galaxy (milky way), whose number was estimated at around  100 (10⁸)-400 million stars (6).

Bacteria together with archae-bacteria form the fundament for the development of complex life. According to the endosymbiotic theory, the ingestion of a bacterium by an archaeon (both procaryotes – single celled organisms without a nucleus) led to a symbiotic form of life from which eucaryotes developed (7). Eucaryote cells possess a nucleus that contains the genome of the organism. They are comparted with organells that perform different metabolic tasks and therefore are considerably more complex cells, which are also 100-10.000-fold bigger than bacteria or archaeon cells. Eucaryotes can be single-celled (e.g. amoeba, malaria parasites), however in contrast to bacteria they can also form multicellular forms of life. Plants, fungus, and animals consist of eucaryotic cells.

First traces of life on earth

The first (disputed) signs of life on earth are around 3.8 billion years old. Anomalies in carbon-isotopes and tubeformation in rock-samples from Greenland were interpreted as signs of oxidative processes in a hydrothermal environment resembling traces that metabolism of nowadays iron-oxidating bacteria leave in rocks (8).

Somewhat surer seems to be the appraisal of slate samples from the Gunflint-Range in Canada. The traces of single celled living organisms were interpreted as traces of 1.9-billion-year-old cyanobacteria (blue algae). Cyanobacteria in contrast to bacteria stand out for oxydating photosynthesis. They therefore may have had an important role in the transformation of the earth-atmosphere from oxygen-poor to oxygen-rich around 3 billion years ago. (Then cyanobacteria would have roamed the earth around a billion years longer than the Gunflint-Range traces testify).

Oxygen accumulation in the atmosphere and in the oceans eradicated the anaerobic organisms that existed. The higher oxygen supply, however, opended up entirely new pathways for evolution. By stepwise oxidation of energy-rich molecules, the emerging oxygen enabled more efficient possibilities for generating energy for live and emergence of life forms.

The following contemplations are confined to multicellular organisms, complex organisms. The single celled procaryotes should nevertheless be acknowledged as important domains in evolution and life on earth even though they will not get the same attention in the following passages as complex multicellular life forms.

Emergence of multicellular life

Multicellular life emerged around 1.5 billion years ago: According to the endosymbiotic theory through phagocytic ingestion of bacteria by another single-celled organism, probably archaebacteria. The ingested bacteria transformed to organells, such as mitochondria (or to chloroplasts in photosynthetically active plants and algae) (9).

When describing evolutionary processes, we are often biased towards the roam of animals (fauna), although plants may be more remarkable from a physico-chemical point of view, because they developed the capability to transform solar energy and use it to generate complex molecules. The photosynthesis that takes place inside chloroplasts, is crucial for all life on earth and also for the atmosphere and the climate. Carbondioxid (CO₂) is being taken up and oxygen (O₂) generated, which is the most important energy provider for animal-life forms (and when transformed to ozone (O₃) also provides the substance for the ozone layer in our atmosphere). Animals are not capable of photosynthesis, although the CO₂ expired by animals can be used by plants for photosynthesis (10).

Metabolic products of animals, however also seem to change the constitution of the atmosphere, with farm animals, especially cows not only producing CO₂, but also methane (CH₄), which is considered to be a potent greenhouse gas

The cambric explosion of life

For a long time, life remained single-celled and small, until in the seas of the Cambrian-period (541-485 million years ago) a downright explosion of life took place: In the 56 million years of the Cambrian, the founding organisms of most multicellular animal and plant strains arose, for example the phylum of the chordatae, among which the vertebrates are a subphylum. The reasons for this explosion of life invite speculations. An increase of atmospheric oxygen in millions of years before the Cambrian may have created the environmental preconditions for the development of energy-intensive forms of being. Mechanisms of natural selection became more sophisticated with hunter-prey interactions that triggered the emergence of more effective sensory organs on both sides (hunter and prey). Hunters that could better detect their prey (e.g. through the uptake of optical signals through eyes) generate a selective advantage over conspecific hunters. Eyes may also provide a selection advantage for prey as they can better detect and deter an approaching threat. Thus, ecological niches with complex interactions between living beings formed. Inside living beings, specialisations of cells, organs and body parts emerged.

The trilobites, who were a very successful class in the phylum of arthropods and lived for around 250 million years in all seas of the world, emerged in the Cambrian. Trilobites can serve for demonstrating the tendencies for specialization with the development of specialized organs and bodyparts. Trilobites had legs for propagation, eyes for detecting light and thus also neural structures for processing optical information from the surrounding sea environment. The transformation of energy was not always a purely biochemical process, but was accomplished by different specialized organs. For the uptake of food (energy), trilobites had oral orifices from which the nutrition (e.g. worms, sea cucumbers) reached a digestive system, where it was broken up, digestible components contained and the rest excreted. Furthermore, trilobites had an exoskeleton that provided stability to the organism, but also protection. Trilobites belong to the phylum of arthropods, like nowadays cancers, insects, millipeds and spiders. Trilobites dominated the seas of the Cambria, but also the seas of subsequent aeons until they fell victim to the biggest mass extinction of complex life around 250 million years ago. On drawn images basend on numerous fossils, their shape reminds me of nowadays isopoda.

Excursus: The precambrian explosion of life

In the middle of the last century, fossils of more than 540-million-year-old forms of complex life were found in the Ediacara mountains of Australia. Consequently, the corresponding life forms must have lived before the Cambrian explosion of life. The importance of the cambrain explosion is not being challenged, as the phylae of nowadays forms of life emerged during this important period. Nonetheless it is remarkable, that around 33 million years before the Cambrian explosion of complex life, already an earlier explosion of complex life had taken place, namely the avalonic explosion of life around 575 million years ago. Fossils of organisms, who lived back then seem unusual even to taxonomers. “Rangeomorpha” fossils resemble fern-plants, albeit they are not related to any modern life form. Rangeomorpha lived attached to the seaground and probably filtered their food from the water. Remarkable is the fractal growth of the Rangeomorpha: Each brench was an identical, smaller edition of the trunk structure. While in nowadays life forms, bilateral achsis-symmetry is very common, organisms of the avalonic explosion typically showed trilateral symmetry. If the avalonic life forms have to be seen as predecessors of the Cambrian life forms or rather as an evolutionary dead-end street is under debate. Most precambric species have gone extinct, however some fossils’ shapes suggest that there may be evolutionary continuity to later forms of life. “Spiriginna” fosils, for example, resemble the trilobites that were so long-lasting and successful later. In 2004 the International Union of Geological Sciences named a new aeon: The Ediacarium (635 – 541 million years ago) reached just before the Cambrian and is now considered to be the period, when multicellular life emerged (including complex life that previously was only conceded to the Cambrian).

The Chordata

Homo sapiens is the only remaining species of the genus Homo, which, together with the genera of the gorillas, the chimpanzees and bonobos and the orang-utans, belong to the family of the Hominidae (Great Apes). So far, our evolutionary relatives still seem to be somewhat easy to understand. The family of the Great Apes belongs to the mammals, which fall into the vertebrate class. Alongside mammals, fish, birds, reptils and amphibiae are verterbrates. The contrary pole are the invertebrates. A common principle of the build-up of vertebrates is their backbone, the Chorda dorsalis. And here we can trace back our ancestry to the Cambrian, 500 million years ago, when the chordata emerged. Homo sapiens is a mammal. All mammals are chordata, but not all chordata are mammals. The line of the mammals emerged from the so-called synapsids in differentiation from the line of the sauropsids, wich gave rise to birds, reptiles and dinosaurs. The differentation between synapsids and sauropsids took place around 300 million years ago. The synapsids (among which the mammals) had quite an unspectacular marginal existence over million of years until the dominating dinosaurs, which belonged to the sauropsides went extinct due to the impact of a comet 66 million years ago.

Water and Land Animals

The Cambrian explosion of the species-diversity of animal life (around 541-485 million years ago) took entirely place in water. Back then, no complex life existed on land, while the seas became more and more alive. (To what extent there were plants on land, to what extent the landflora preceded the land fauna for million of years is under dispute (11, 12)).

The Invention of the Egg (Amniots)

Around 350 million years ago, at least amphibians who, although they spent most of their time in the water, could do expanded landwalks close to their water habitat. However even amphibians that could exist for long time periods outside water, relied on the water habitat for reproduction. The step from amphibians to land vertebrates was eventually made possible through the emergence of water independent eggs. These had an eggshell, were watertight and could be laid on land. The internal egg membrane, which surrounds the fetus, is called “amnion”. This evolutionary innovation – the egg – became eponymous for the newly emerging group in the animal kingdom: The amniots. The amniots were able to live entirely on land (which did not mandatorily mean giving up proximity to water). The aquatic environment needed for the offspring to emerge and grow was packed into an egg. The shell, which initially was rather leathery (just as it still is in nowadays reptiles) later also occurred as calcified hard-shell. It protects the fruit from drying out, from infections and from hungry predators. At the same time the porose eggshell and the underlying chorionic membrane allow metabolic exchange with the world outside the egg (e.g. influx of oxygen and efflux of carbondioxid). The amnion is the inner membrane, which surrounds the inner space of the egg, the amniotic cavity, in which the embryo swims in amniotic fluid. Thus, the amniotic cavity can be regarded as an aquatic habitat packed into an egg, which enables the embryonic development independent from water. The amniots split into two very successful vertebratelines: the sauropsids and the synapsids. The mammals belong to the synapsids and the reptiles, birds and the dinosaurs belong to the sauropsids. For a long time, the synapsids (and with them the mammals) existed in the shadow of the dinosaurs, who back then dominated complex life on earth. The extinction of the dinosaurs due to a comet impact 66 million years ago, opended up a lot of ecological niches to the few surviving species of mammals on land and in the seas.

Excursus: The development of the continents between the “invention“ of the egg (350 million years ago) and the extinction of the  dinosaurs (66 million years ago)

During the Perm period, 300 million years ago, the supercontinent Pangea had emerged by the fusion of the southern continent Gondwana with the northern continent Laurrussia. The formation of such a supercontinent led to a reduction of coastal habitats, which were always well suited for life in the past. Now there was an endless ocean and on land large continental areas that were dominated by desserts, as rain hardly reached inland and low-pressure zones at the coasts drew hot and dry air from inland areas.

The Perm-Trias fringe around 250 million years ago is considered as a transition period from the Palaeozoic to the Mesozoic era. This transition was marked by the biggest mass-extinction event in the history of the earth around 252 million years ago (13). Around three-quarters of the species living on land and 95% of marine species were lost, among which also the last remaining species of trilobites (that had survived previous mass-extinction events) and lots of insect species, which are usually less affected by mass extinction events. The exceedingly successful class of the trilobites thus was lost forever after they had dominated complex life on earth for around 300 million years (14). After this “tabula-rasa”-event, around 245 million years ago, the first predecessors of the dinosaurs, the archaeosaurs, appeared. The world of the dinosaurs was first emerging under the conditions of the supercontinent Pangea, which then drifted apart (starting around 230 million years ago).  Pangea was a conglomerate of all nowadays known landmasses, a dry and hot supercontinent with few inland water, but surrounded by an endless primeval ocean. With the upcoming brake up of this continent, the conditions for life improved as several smaller landmasses brought about more coastal habitats with a more humid-tropical climate on land. The continental drift, however, also triggered frequent and large geolgical events. Around 252 million years ago, the Perm-Trias mass extinction (that preceeded the dawn of the dinosaurs, so the dinosaurs were not yet there to be affected by it) happened within a short period of only 60,000 years. The Siberian Traps are gigantic areas (millions of square kilometres in Russia) of volcanic, 3 km thick flood-basalt deposits in layers that represent the time of the mass extinction around 252 million years ago. These gigantic masses of magma emerged in a very short time (in geological terms) of only a few hundred thousand years (15). The big mass extinction 252 million years ago was a consequence of volcanism. Gigantic carbonfields were set on fire increasing the atmospheric CO₂ content which led to an acidification of the water habitats that became anoxic and an overheating of the whole athmosphere.

Around 201 million years ago at the transition from Trias to Jurassic, there was another (smaller) mass extinction of complex life. After this smaller mass-extinction the age of the dinosaurs could fully unfold, now from the beginning of the so-called Jurassic period (think of the “Jurassic Park” films) and came to an end with the mass extinction around 66 million years ago, which was caused by a comet, whose crater can be found in the Caribbean Sea right at the Mexican peninsula Yucatan. The drifting apart of the landmasses, especially the westdrift of the American continent with opening of the Atlantic, led to separate development areas of the dinosaurs on different continents.

Antarctica and Australia together with Africa had separated from the supercontinent Pangea around 200 million years ago. Australia separated around 45 million years ago from the Antarctic continental plate (and became the kingdom of the marsupials). The formation of mountain ranges is commonly linked to continental drift. The alps were formed around 53 million years ago, when the African plate drifted into the Eurasian plate and the largest and highest mountain range, the Himalaya, was formed around 40 million years ago, when India coming from the south crashed into the Eurasian landmass. (So, there were no alps and no Himalaya, when the dinosaurs ruled the world until 66 million years ago).

Interestingly, during the dinosaur time (between 200-66 million years ago) most oil developed that we exploited and burned in unbelievable amounts in less than 300 years since the 19^th century. The oil, however, did not originate from perished dinosaurs, but rather from algae that decayed to sludge. By overlaying and subsidence such carbon rich algae sludge underwent pressure and temperatures of deeper layers turning the sludge into liquid (oil) and gasiform (natural gas) state. The big extinction 66 million years ago wiped out the dinosaurs, however some sauropsids survived: Birds and reptiles.

Furthermore, Megazostron survived, a small shrew-like, fured animal of the synapsid group, which before was running around the feet of the mighty dinosaurs, or was obliged to hide from these dangerous gigantic saurians.

The Rise of the Mammals

The small mammals that had survived the mass extinction 66 million years ago, lived from insects (of whom also a lot of species survived the mass extinction). Now, that many previously occupied ecological niches had become vacant, the mammals could comme out of their hiding and conquer the earth on land and even in the fish dominated oceans. The sauropsides survived in birds and reptiles. Initially the small insect-eating mammals had few enemies to fear until the first carnivores emerged from their own ranks. Some shrew-like species were becoming tree dwellers that later on turned into predecessors of primates. Primate develpment was fostered by a warm period 56 million years ago (just 10 million years after the comet impact that wiped out the dinosaurs). During the Paleocene-Eocene-Thermal-Maximum (PETM) the poles were ice free and the whole earth was a warm place with humid-warm climate, tropical vegetation and dry desserts. The mix of tropical climate and high carbon supply made plant life flourish turning the landmasses in to “green hells” (but maybe heaven for tree dwelling primates). For land mammals and reptiles the PETM was a very good time. The predecessors of the primates for example developed very well. After the extinction of the dinosaurs, some of the tree dwelling shrew-like megazostron-lines, shifted their eyes to the front and transformed their hands and feet into climbing and gripping tools.

Excursus: Paleocene-Eocene-Thermal-Maximum (PETM), 56 Millionen years ago

„Only” 10 million years after the extinction of the dinosaurs during the Paleocene-Eocene-Thermal-Maximum (PETM) around 56 million years ago the CO₂-concentration of the atmosphere increased from around 800 ppm (parts per million) to over 2000 ppm in a very short period of around 10,000 years and the temperatures increased by 5-8 degrees Celsius (the preindustrial CO₂-concentration before 1750 was around 280 ppm and nowadays it is at over 415 ppm). Where did this rapid increase of carbon-greenhouse-gases come from? There are different theories, all involving the release of fixed carbon. Large forest fires could release a lot of carbon, likewise burning carbon or peat bogs. Rising temperatures could have led to an additional release of methane from permafrost or from methane-hydrate layers at the continental shelfs, thus further increasing the greenhouse-effect. In geological terms, the PETM did not hold very long. Already after 3 million years, around 53 million years ago, temperatures fell again and 34 million years ago the poles were entirely covered with ice again. How this happened is also under debate. Chlorophyl-containing water-plants (Azola), may have overgrown the oceans and may have bound CO_{2  ,} and after dying off and sinking may have taken it to the abyss. The deprivation of the CO₂ would have led to cooling of the atmosphere.

Old and New World Monkeys

Around 180 million years ago, during the bloom of the dinosaur world, Pangea started drifting apart. For the development of the mammals 2 separated main landmasses emerged and this is why nowadays we call American monkey species “New World monkeys” and Eurasian-African species “Old World monkeys”. The oldest monkey fossils that were found in America are around 36 million years old. Although not entirely sure it is assumed that the New World monkeys’ ancestors were Old World monkeys. These somehow must have made it over the Atlantic, maybe on swimming mangrove conglomerate rafts, considering that the Atlantic during the Eocene (around 56-33 million years ago) was smaller than nowadays. In the following 30-40 million years, the continents of the Old and the New World driftet further apart making the Atlantic become wider and wider until the distance had become so far that two entirely separate evolutionary networks emerged. Among the Old World monkeys, we also find the apes, to which man belongs. 

On the African continent the Old World monkeys flourished and around 25-30 million years ago the apes (Hominoidea) emerged as line of its own from the Old World monkeys. The characteristic feature of the apes is their taillessness. Taxonomicially, apes are a superfamily in the order of primates in the class mammalia in the phylum chordata. We humans are apes. Apart from man, gorillas, orang-utans, chimpanzees and – often forgotten- gibbons belong to the apes (gibbons are also tailless). And why do we frequently forget the gibbons? Because the apes (Hominoidea) are a superfamily, to which we count, apart from the gibbons family, also the family of the extinct proconsul. And the Hominidae (gorillas, orang-utans, chimpanzees and men). Hominoidea, Hominidae