. . . e v o l u t i o n e m . . .

 

         taking a fresh look at evolution

Rainforest Apes from Canids?

Racoon

African Hunting Dog

In this article I want to propose a new idea: that apes are not directly related to monkeys or other primates, and similarities in their form are merely features of evolutionary convergence. Instead, I will describe a new pathway for Rainforest Ape evolution; this idea was first conceived as a result of comparing brain morphology. That research suggested a possible route of rainforest apes evolution from a predatory canid (African hunting dog). This notion may seem preposterous at first, if not insulting to the ego, but I believe this line of evolution is demonstrated by similarities in brain architecture between apes and canids.

 

Brain architecture follows a linear evolutionary pathway which involves incrementally added faculties. By contrast, other organs like skeletal structures and dentition can change their form profoundly over short periods of time. For this reason, much of the early classification of animals is likely to be erroneous. In the light of a new appreciation of the process of reversion, animals can switch aspects of their form quite dramatically. Consequently, I believe, no longer should animals be related together in groups by such similarities as say, the number of toes, the type of dentition, or the flatness of their faces and the way they move about in trees.

 

Predatory Hunting Dogs have roamed the savannahs of Africa for at least 40 million years. These animals were perhaps the forerunners of a very successful family of mammals - the Canidae which nowadays includes wolves, jackals, foxes and dingos, to mention a few. These original members of the canid family were likely derived from scavenging hyena type ancestors.

 

Predatory animals, generally, are much more intelligent as individuals than their grazing or scavenging equivalents, because successful hunting demands group coordination and elaborate repertoires of hunting behaviour.

 

Wild hunting dogs still exist on the open savannahs of Africa - although man has reduced their populations and distribution to such a dangerously low level that they now face extinction. Aside from this, it is evident that the hunting dog way of life has been successfully sustained for many millions of years without need for change. Another example of Stasis. At times, during this period however, there will have been  severe constraints  (perhaps due to overpopulation) on some groups of these animals with the result that some may have needed to change their habitat to continue to survive. Some of these dogs could have changed their hunting grounds to a nearby rainforest habitat and got themselves established there.

 

To successfully adapt to this new habitat, however would mean many changes in behaviour and form.

 

Hunting would need to be carried out on an individual basis rather than in groups because hunting in packs can only occur successfully in a relatively open environment.

 

Ground based prey would be targeted first as those living in the trees would be inaccessible.

 

The First Stages

 

So how did a group of these canids adapt to an arboreal lifestyle and begin the process of primatisation (taking on monkey-like characteristics)? It might have happened like this.

 

A hunting dog may have leapt up onto the branches of a tree in pursuit of its prey but could not go no further. While it was up there, another prey animal passed by below and the dog was able to drop down and seize hold of it.

 

A successful manoeuvre like this would be repeated time and time again and others would begin to copy it. The technique would be demonstrated to offspring and the strategy would be passed onto many successive generations.

 

So already, behaviour patterns will have begun to change quite considerably, for the hunting dog pioneering the new rainforest habitat. Now we can start to think of them as rainforest hunting dogs. They are on their way to becoming a new species of hunting dog as they are developing in isolation of the ‘true’ hunting dogs of the savannahs.

 

Future generations of these animals would produce variations wherein some were more able to climb further up into trees and perhaps reach alternative food resources such as snakes, chameleons and lizards. There would be natural selection for those individuals with these abilities over those which had not and, perhaps, individual animals became smaller in size, to fit the demands of the new environment.

 

There are several extant species which exhibit this intermediate format - somewhere between ground predator and primate. Examples of these are the Racoon (Procyon lotor), Kinkajou (Potos flavus), and Madagascan Fossa and so viability of this way of life is evident. In time, perhaps millions of years, selection for features which are essentially primate-like will come about in these animals. This is because primate characteristics and forms are the best suited for the maximum exploitation of arboreal life.

 

Let us have a closer look at some of these modern intermediates.

 

The Racoon (Procyon lotor)

 

Our pioneering rainforest dog, at the stage described above, could have had traits similar to the racoon. They are quite capable of climbing up into trees. They are relatively small (around 30 inches in length) and some aspects of ‘primatisation’ are already present. These include the five fingered  and manipulative hands and the long and narrow hind feet (plantigrade) which rest flat on the ground - as in all primates. Diet is omnivorous and mainly relates to resources found in trees including fruit, eggs, nuts, insects and rodents.

 

The Kinkajou (Potos flavus)

 

Kinkajous are of a similar size to the racoon. They are more dedicated to life in the rainforest canopy than the racoon which roams at ground level too. Hence, as one would expect, they are endowed with characteristics which are more monkey-like. They have shorter snouts, forward facing eyes, rounded ear lobes, and a prehensile tail. They also have, the primate-like long fingered hands and long feet.

 

The brain morphology of the kinkajou is comparable with that of the racoon - and so it could be that Kinkajous are just further along the path of primatisation than racoons.  It is quite possible that kinkajous are derived from racoons as both species are distributed in the same Central American region.  

 

A Closer Look at Primatisation   

 

In the diagrams below the skeleton of a dog  illustrates the long carpals and tarsals of the digitigrade form. Dogs, like many other mammals and birds stand on their toes. Primates and some mammals like the racoons and kinkajous, mentioned above, have short carpals and tarsals and are described as plantigrade.

 

 

In the process of primatisation, the carpals and tarsals are reduced to form long flat feet and hands. I have digitally modified the original dog skeleton to show this in the next illustration.

 

 

I have also orientated the skeleton into an upright stance, rotating the cranium to a position at right-angles to the vertebral column. There are also other skulls depicted, showing foreshortening of the snout. To complete the primatisation into an ape, I have removed the tail vertebrae and  depicted the vestigial tail (pigostyle).

 

Foreshortening of the Snout

 

The following is a stage by stage digitally modified illustration to show how the  characteristics of primates’ faces can easily emerge from a canid profile.

 

By examining various breeds of dogs, we  can easily understand that profound changes in skull architecture can come about in a relatively short time. Compare the bulldog skull with that of the Saluki:

 

 

 

    Bulldog  (courtesy BoneClones)                                       Saluki  - (courtesy BoneClones)

 

So bone architecture is quite adaptable within certain parameters.

Rainforest Apes have, to a great extent, retained the canid dental format, albeit in a much more compact mouth. The large canines of male gorillas could have been retained for threatening behaviour against predators or perhaps used  as nut or pod cracking devices.

 

The long snout of canids is basically a housing for a highly developed olfactory apparatus. Primates do not have a need for such an elaborate and effective sense of smell, and so this faculty has been trimmed down along with the length of the snout. Primates rely on visual cues more than olfactory ones when procuring food.

 

Primates have forward facing eyes in which the field of vision of each eye overlaps with the other, and this gives a depth of vision ideal for gauging distances. This is particularly important in assessing the distance to jump or swing to the next tree or the proximity of a predator. The characteristic upright stance of primates when sitting also allows them to quickly rotate their heads almost 360 degrees to view the surroundings.

 

In a similar way, owls are upright in their stance - and can rotate their heads on a vertical axis - so this positional attitude must be advantageous.They too have forward facing eyes.

 

This configuration allows an all-round vision with no blind-spots caused by the rear part of the animal’s body.

 

Brain Comparisons

 

These coronal sections of various mammal brains are courtesy of the brainmuseum.org.

 

Canid

 

There is no specimen  of the African hunting dog available - and so I have chosen the Coyote (Canis latrans) as a representative Canid.

 

 

 

Chimpanzee  (Pan troglodites)

 

The Gorilla brain is not represented as a coronal section and so I have chosen the chimpanzee Pan trogladites.

 

 

 

Human (Homo sapiens)

 

The above three brain sections show the same development of the dorsal region of the brain architecture with the characteristic ‘Lorraine cross’.

 

Hyenas are notably less intelligent than hunting dogs and the brain sections comparisons appear to confirm this - when you note the lesser degree of convolutions of the hyena brain. The coyote brain is much more convoluted on its peripheral areas than the hyena’s. In fact the coyote brain architecture is more like the chimpanzee’s than the hyena’s.

 

The brain sections below have a more rudimentary development of the dorsal region of the brain architecture - ‘the single cross’.

 

Hyena (Crocuta crocuta)

 

 

Racoon (Procyon lotor)

 

The Racoon seems to be one stage on from the Hyena in its brain development

 

 

Kinkajou (Potos flavus)

 

 

Lemurs have an even more rudimentary dorsal architecture:

 

Ring-tailed Lemur

 

Note the difference in architecture of the lemur brain. And note that the Rhesus monkey brain is more akin with that of the racoon than the chimpanzee.

 

Rhesus Monkey

 

 

Titi Monkey

 

The brain architecture of the South American Titi monkey is surprisingly similar in architecture to the Ring-Tailed Lemur.

 

 

From the above I believe it is clear that we owe a lot of our intelligence to the humble African Hunting Dog. Many aspects of canid behaviour are similar to ours.

 

We chose alpha  males for our leaders and show similar obedience to their comands and dictates.

 

We show social cohesion among groups; hunting dogs provide food for the injured and the aged.

 

Dogs in general show many emotions, compassion, jealousy, rivalry which no other mammal other than apes show with such intensity.

 

The genome of humans and wolves (Canis Lupus) have been mapped and now await detailed comparison. When other primates are also mapped I believe it will be possible to confirm the canid to ape evolutionary route.

 

Already some genes appear to be unique between canids and apes.

 

Genes associated with the regulation of transcription in embryonic cells produce HMGA proteins.  These genes should cease activity of expression in adult tissues but in cases where they are still expressed, cancerous tumours are often associated with these proteins. So it appears that an error in the mechanism of gene control during development occurred at the canid stage - as apes (humans) and dogs both share the same types of cancer - such as thyroid, prostatic, pancreatic, uterine cervical and colorectal cancer. (H. Murua Escobar et al, 20005).

 

 

 

 

       

 

 

 

 

Suggested Pathways for other Primates.

 

1. Lemurs  of Madagascar

 

Lemurs are unique in that they only exist In Madagascar and some nearby islands.

This suggests that these animals evolved during the time that Madagascar has been separated from  the continent of Africa.

 

Separation from Africa was likely caused by the stretching of the  Earth’s crust - and not by new ocean bed formation as in the case of  Australia  (also a former neighbour of East Africa).

 

Madagascar’s proximity to Africa, some 400 km, suggests a  fairly recent separation. It appears, though, that  Madagascar has moved away from Africa ( the Mozambique coastline) in  a north-easterly direction, actually moving a distance of some 800 km.

 

Stretching of crustal surfaces are in the order of 1 - 2 cm per year. So Madagascar could have been attached to Africa between 40 and 80 million years ago. However, there may have been a causeway linking  the island as little as 30 million years ago, if one considers that sea levels may have been much lower, particularly during major glacial  periods.

 

So lemurs are likely to be derived from  African species which inhabited the island before full separation. These were likely to be small tree dwelling mammals like Bush Babies (Galago) and larger ground based mammals.

 

The Madagascan Fossa (Cryptoprocta) could be a relic of the original African species. Its form, a  curious mixture of both cat and dog characteristics, ties in nicely with this notion. It is likely that all these carnivores including hyenas evolved from an ancestral species which roughly resembled the format of the mongoose. Comparing brain morphology, (coronal sections) seems to reinforce this suggestion. Compare the brains of hyenas, civet, badgers, weasels and mongooses and they all show a similarity.  I would expect the Madagascan Fossa would also have a similar brain architecture. The  Fossa, if it is a relic of African fauna some forty million years ago, could have been something like the progenitor hub of hyenas, aardwolfves, hunting dogs, and all of  the cat family.

 

Lemurs could  have come about by the process of  ‘primatisation’  of one of the original African ground dwelling animals. Lemurs are therefore not necessarily archaic prosimians at the lower end of the our evolutionary tree - as we were led to believe by taxonomists; they may have evolved quite recently. Their monkey-like features are more than likely converged in the process of ‘primatisation ‘ described elsewhere.

 

 

Primatisation - another  example of the process - but  this time in a marsupial.

 

The Koala bear (Phascolarctus cinereus) shows some aspects of primatisation. Its closest relative is the wombat (Lasiorhinus spp ). which is a ground dwelling animal.

 

The koala has an opposing thumb and fore-finger and fingerprints on the ends of each digits. These are typical monkey-like adaptations for gripping branches. They are plantigrade in their hand formation and  less completely plantigrade in their feet structures. They have flat faces and forward facing eyes and can sit upright like monkeys.They do not have long tails like monkeys  - but their relatives - the wombat do not have long tails either.

 

Koalas have not evolved universally jointed arm sockets - like primates - but this could be due to them being only recently adapted to tree dwelling. Alternatively, the reason could be that koalas are very sedentary and spend much time in one tree. Their diet is exclusively the leaves of the eucalyptus tree- and so there is no need to wander from  tree to tree to find different foods as monkeys do.

 

We know that marsupials are very distantly related to primates and so there can be no confusion into thinking that they are somewhere on the ladder of primate evolution. However, they show that the environment - tree dwelling - can  fashion characteristics which are essentially primate-like. This is pure evolutionary convergence.

 

In a similar way, the different environments throughout Australia have fashioned a primordial marsupial into many different forms which correspond  with the true placentals. The now extinct carnivorous Tasmanian Wolf (Thylacinus) converged to look very like a wolf.

Dasyrus  has converged to look like a small cat. The flying phalanger (Petaurus) is like the flying squirrel. There are also marsupial moles, marsupial mice, marsupial anteaters and so it is not surprising we have a sort of marsupial  ‘monkey’.

 

 

 

Kinkajou