When should a story begin? If it’s a biography, common practice seems to be to recount the lives of the subject’s parents, although one might also talk about a more distant background. If I think about my own life history, it feels like a mistake to focus too much on background because it can easily drift into nationalism and racism. Many online discussions about genome analysis undertaken on White people seem to be embarrassed about recent Black ancestry and tend to be couched in terms of them being errors due to small amounts of data, which is really sad. On the other hand, it’s also possible for a White person in particular to appropriate swathes of Black or other Disneyfied ethnic identity for themselves for some kind of cringeworthy cool factor. Since my own ancestry is substantially Scottish, I could easily slot myself into tartanry. This kitschiness is very much to the fore and has been going on for two centuries now. Wikipedia describes it as “twee, distorted imagery based on ethnic stereotypes”. Two images of this in particular come to mind, both rather similar. One is of a tourist picking up a soft toy of a tartan mouse in Inverness and saying ,,Eine schottische Maus”, and the other is of a plethora of tartan Nessie plushies in a Loch Ness visitor’s centre gift shop. On the one hand, it’s quite embarrassing, but on the other one can understand the need to turn a somewhat honest penny in a remote location with few economic opportunities, and I imagine the same love-hate relationship with tourism I used to experience in Canterbury would be reproduced there. You need the tourists but they can be almost immediately tiresome.
In the case of human ancestry, we are all currently the product of at least two parents, who are in turn the product of two parents and so on back to a point where we appear to have more ancestors than the human population of the planet at the time. In fact you probably don’t even need to go back that far to experience that quandary, as people didn’t used to move around as much as many of us do nowadays. Many of my ancestors would probably have ended up marrying someone in the next village, or even the same village, and you can easily get back to the point where your family tree didn’t seem to have branches. This applied as much in West Afrika as it did in Argyll, although people did become displaced from both locations by events such as the Atlantic and Barbary Slave Trades, the Highland Clearances and the Famines. These mixtures have brought the common ancestors of all humans forward by millennia, such that it’s now estimated that our most recent common ancestor lived in the late Bronze Age, which when one considers how isolated certain groups are, such as in Papua or the Amazon, is quite counter-intuitive, but this reflects what has happened in recent centuries rather than further back.
As one ascends the global family tree, the generations become increasingly diagonal. Because most couples have at least two children survive to have children of their own, their age differences add up and start to skew the ages of people who, for us descendants, appear to be in the same generation. An extreme case of this might be a mother who has a child at twenty and another at forty, which is effectively a whole generation apart. In that case only two generations are needed for people in the same family to have a big enough age difference to be grandchild and grandparent, though not in practice of course. Even a year’s difference can achieve this within twenty generations. This also means that when one considers one’s ancestry, the range of possible dates of birth of unknown ancestors widens the further up you go. What would eventually happen, with perfect knowledge of the world’s population, is a family tree with multiple instances of the same individual in many places and different generations relative to oneself. The consequence of all this is that we are all part of the same human race.
This makes a lot of sense when considering evolution. It’s easy to imagine evolution as a sudden change in the population, and certainly point mutations do lead to this, but in fact what seems to make more sense is for a trait to begin in a certain individual and then spread across the species, and another trait to begin elsewhere and similarly spread, until you end up with a situation where either both traits, and of course many others, have spread throughout the population, leading to it having become a new species, or only some of them have, leading to either a ring species or the separation of the population into two or more such species. For solely sexually reproducing species, there cannot be a single founder of a new species, so for us, going way back into the past, it has always been a question of entire populations evolving together into new species.
A few days ago, I communicated poorly with someone by saying that our ancestors arose in North America, because they thought I meant hominids, the family including orang-utan, humans, gorillas, bonobos and chimpanzees, had arisen there. This is by no means the case of course, although there used to be a school of racialist anthropologists who believed in polygenesis: that the ancestors of surviving humans were already several different species. This would make humanity a grade rather than a clade – a group of organisms with the same kind of organisation in terms of anatomy and physiology which are, however, not descended from a common ancestor with those characteristics. These are seen a lot in biology. For instance, reptiles, when considered as a group of scaly air-breathing vertebrates whose bodies are at the same temperature as their surroundings when at rest, constitute a grade if some of the extinct “mammal-like reptiles” are included and birds excluded. Likewise, the mammal-like forms themselves consisted of several parallel lines developing the same kinds of characteristics but not from a common ancestor, and even hominids have done this. There used to be some confusion around a species of ape who had a number of particularly humanoid characteristics living in Europe before the first of our immediate ancestors got there, suggesting that we had evolved in Europe. The fact is that related species are wont to develop similar traits due to having similar genes and sometimes being in similar ecological niches.
But I actually meant omomyids. I think I’ve mentioned these before in this blog, so I won’t go into super depth on this, but back in the Eocene, 56-34 million years ago, primates were chiefly found in North America, and were of two main types: the adapids and the omomyids. Adapids were more lemur-like but less specialised, lacking the comb-like incisors and grooming claws found in many of their descendants. Both groups are themselves descended from the plesiadapiformes of the Palæocene, several million years previously, who looked like this:
Thus when I said “our ancestors”, I was referring to early primates, not hominids. It may be a little surprising that primates first appeared in North America, a continent from which non-human primates are almost absent (there are spider and howler monkeys in Mexico), but this distribution change is not unusual. Camels first evolved in North America around the same time as omomyids, but are now found on every continent except North America and Antarctica, although the Australian population is feral. Likewise, the earliest horses evolved in North America, spread to South America after the continents joined, then both American horse genera became extinct at the end of the last Ice Age, leaving them in Afro-Eurasia alone. This may, incidentally, have had huge consequences for human history as the domestication of the horse and the absence of exploitable beasts of burden in the Americas seems to have led to a major split in the types of culture which arose in those continents compared to Eurasia. There is in fact something of a pattern here, of particular mammalian clades evolving in North America, spreading elsewhere and then becoming extinct in the continent on which they originated. At the time, Earth looked roughly like this:
I chose a particular cut-off point here in a sense, because clearly forms ancestral to the primates would not initially have been native to North America, but the point was to contrast them with possible prehistoric Antarctic mammals. The Eocene was an extremely hot period, more so than any time during the reign of the dinosaurs, and consequently Antarctica was by no means snow-bound or ice-covered. The question was asked of whether there had ever been indigenous Antarcticans, to which the answer is not only “no”, but also that there haven’t even been indigenous Antarctican primates. One of the big divisions among mammaliforms is the Boreoeutheria versus the Gondwanatheria. As the name suggests, Boreotheria first evolved in the north, and share the primitive feature of males having scrota. They evolved about four million years before the Chicxulub Impactor arrived and were ancestral to the Euarchontoglires, a superorder including colugos, tupaias, rodents, lagomorphs and primates, as well as the Laurasiatheria, including fissipedal carnivores, seals, pangolins, odd- and even-toed ungulates, whales, hedgehogs and their kin, and bats. By contrast, the Gondwanatheria were native to the southern hemisphere, including Antarctica, may not even have been true mammals as such, and if they were, may have been a separate group of mammals and arguably the most successful and definitely the most durable, group, the multituberculates, mentioned before on here. Another southern group of mammals hard to place in relation to other placentals is the Xenarthra, who include sloths, armadillos and anteaters. There are also the Afrotheria, which include aardvarks, elephant shrews, some other shrew-like mammals, hyraxes, elephants, dugongs and manatees etc, and various extinct groups. Besides all these, there are of course the marsupials and monotremes (surviving egg-laying mammals). Hence Antarctica did seem to have marsupials and possibly some other mammals native to the southern hemisphere.
Back to primates. Omomyids and adapids had separate fates. It’s common for creationists to ridicule the established scientific paradigm by stating that the claim is that we evolved from monkeys. This is “not even wrong”, as the phrase has it. The earliest simians were the omomyids. They were somewhat tarsier-like, and although they began in North America, they spread into Eurasia. Tarsiers themselves are somewhat specialised, being nocturnal and having large eyes which are impossible to move by themselves, so their necks turn round almost all the way, which has led to them being perceived as spooky. They’re also kind of carnivorous, but like all simians (and no other primates) they need vitamin C in their diet, so I presume they must also eat fruit or some other good source. Omomyids generally had smaller eyes, were sometimes diurnal and had less flexible necks. Tarsiers have basically been the same for 45 million years now, so if you want a rough approximation of what our ancestors looked like, they wouldn’t be far off.
All monkeys, Old World and New, are descended from omomyids. The peculiar claim that apes are not monkeys is a bit dubious because cladism insists on creating groups consisting of all descendants of a common ancestor, so in that sense we are still monkeys. We’re also apes, and apes are monkeys. This is a little awkward, because of the sloppy use of terminology that tends to call non-human apes monkeys. Technically that’s correct, but they’re tailless monkeys with torsos wider than they are thick. Another issue is with the racist use of the words to imply inferiority, meaning that although biologically we’re monkeys and of course also apes, it may also have offensive connotations. One answer might be to reclaim these terms, but as the world’s Whitest woman I can’t really go around saying I’m doing that for their sake, any more than I can spell “Afrika” with a C in spite of the fact that I have my doubts about the rationale of spelling it with a K.
The question arises of what happened between the omomyids and the emergence of hominids. This would be the Oligocene. In the Miocene it’s well-established that there was a great variety of different kinds of apes and it’s therefore difficult to trace human lineage through that thicket of similar forms. Before that, however, was the Oligocene. A significant animal from this time is Ægyptopithecus zeuxis:
This primate lived before the ancestors of Old World monkeys and the ancestors of apes separated, around thirty million years ago. Before this, there was an Old World primate called Oligopithecus who was more like a marmoset or tamarin than today’s Old World monkeys, and this raises the issue of how they got there. The split occurred about forty million years ago, which is in the Eocene, and their arrival in South America is controversial. Although there were primates in North America at the time, which would’ve meant convergent evolution with Old World monkeys to some extent, it’s more likely that they travelled over the Atlantic on rafts of vegetation, bearing in mind that at that time the ocean was narrower and the rainforests in Afrika still existed further north. Hence sadly, monkeys did not evolve twice. If they had, it would make the idea of humanoid aliens slightly more plausible. The New World monkeys themselves began to diverge from each other around 27 million years ago and now comprise five families. Although the smaller marmosets might be thought of as having evolved from larger monkeys to occupy the vacant prosimian niches in the Amazon, in the light of the likes of Oligopithecus it looks more like they were the more primitive forms and the reason they’re more prosimian in size is that they’re genetically closer to them, although this is just my guess. It does make sense that it would’ve been easier for smaller primates to survive being swept across the ocean, but there were other primates which initially made a living there but soon died out, such as the Afro-Arabian-Asian parapithecoids, who were very monkey-like.
Primates used to be a lot more widespread than they are today. There were European native primates such as Dryopithecines, who could’ve been closer to Afrikan apes, orangutan or perhaps equally related to both. They’re quite neat, as they’re apes who dominated Europe before humans reached here. They were roughly bonobo-sized and ate fruits and leaves. Later on, they may have built up fat reserves in the summer to tide themselves through the winter.
As for our immediate hominin ancestors, I should hold my hands up here and confess to being an adherent of the aquatic ape hypothesis. The standard narrative is that some apes became more humanoid during the drying period of the late Miocene and the Pliocene, being forced to survive on the Afrikan savannah. This is not what I believe. In order to explain why this could not have happened, I need to talk about endogenous retroviruses. These are stretches of genomes which used to be viruses, which have transcribed their genomes into those of other organisms. At some point in the Pliocene, baboons started to shed a virus of this type which infected all other primates in Afrika. No Asian or South American primates have this area of genome, and all Afrikan primates do have it. Humans do not have it, although up to eight percent of our genomes are made up of retroviral code. This is from before the appearance of genus Homo. It appears to support an Asian origin for our ancestors, but it’s equally compatible with them having been isolated on an island off the Afrikan coast. The oldest stone tools are found in Ethiopia and seem to have spread south. There are also a number of adaptations in humans which suggest we spent a lot of time in the water, such as:
- Near-hairlessness.
- Insulation from fat deposits, including floating breasts more accessible to young in the water, along with long scalp hair affording protection from the Sun and a handhold for babies.
- A hymen, protecting the reproductive system from sand.
- The presence of a diving reflex, where metabolism and heart rate slow when immersed in water.
- Breath control.
- Face to face lovemaking, found mainly in marine mammals.
- Downward-facing nostrils.
- Erect bipedalism.
I’m not being thorough here. This is just a selection of adaptations which suggest we had an aquatic phase. However, this doesn’t mean we lived in the water like dolphins. It’s more like we lived on the beach and escaped into the water from potential predators, kind of like we were semi-mermaids. It’s also possible that elephants went through a similar phase, as they still have a lot to do with water. Moreover, early stone tools were made from pebbles, as found on beaches. Proboscis monkeys also have similar adaptations, such as their noses, and spend some time in water.
I think that’s all I really want to say today. It’s a bit spotty, but I’ve tried to highlight some of the less well-known bits of the history of primates. There’s a lot of other stuff, such as the orang-utan relatives who lived in the Himalayas and the recently extinct northern Chinese gibbon species, but this will probably do for now.
A Box Of Chocolates 