Category: Primatology

Some general information on primate locomotion

The vast majority of primates live in tropical climates and forest environments. Some species also live in savannah-type environments or at higher altitudes. This is the case, for example, of the Barbary macaque, which lives in the Atlas mountains and on the promontories of Gibraltar. We can also mention the Roxellan Rhinopithecus, which lives on the Tibetan plateau, in a sometimes snowy environment. If you’d like to find out more about primates, we invite you to read our previous article. Thus, primates live both arboreal and terrestrial lives. This diversity of occupied environments leads to great diversity in primate postural-locomotor repertoires. Unlike most other mammals, primates can practice different modes of locomotion within the same repertoire. 32 posturo-locomotor modes have been identified, and primates are commonly grouped into ten major locomotor categories:

• Vertical jumpers and climbers
• Brachiators
• General arboreal quadrupeds
• Semi-terrestrial quadrupeds
• Land quadrupeds
• Quadrupedal knuckle-walking
• Slow climbers
• Claw climbers
• Biped
• Some American primates also have a prehensile tail, which they use as a fifth limb to suspend and stabilize themselves in trees.

These different locomotor modes are characterized by anatomical adaptations to the skeleton. However, we have to be careful when we talk about these adaptations. Indeed, primatologists now know that it’s not necessarily the time spent on the main mode of locomotion that best reflects skeletal adaptations. For example, the chimpanzee is defined as a knuckle-walker according to the broad categorization mentioned above. Nevertheless, most of the chimpanzee’s skeletal adaptations are not for this quadrupedal walking, but for suspension and vertical climbing, which it also practices. Categorizing posturo-locomotor modes helps us to define them. Nevertheless, it’s important to bear in mind that each primate species has its own way of doing things.

In the rest of this article, we’ll take a look at some of these modes of transport.

Vertical jumpers and climbers

Tarsiers, for example, use this mode of locomotion. The term “jumper” comes from their movement through the trees and on the ground in successive leaps. They can leap a distance that is up to forty times greater than their size! The term “vertical climbers” derives from the fact that tarsiers climb trees vertically, straightening their backs and spreading their limbs to cling to the trunk. The main adaptations to this type of locomotion are found in the postcranial region, and more specifically in the lower limbs, which are particularly elongated. In fact, they are 1.5 times the length of the trunk, providing support for propulsion during jumps.

Brachiators

Brachiation is defined as bimanual progression over several meters between two structures without using any other type of locomotion and without using the support of the tail or hind limbs. This type of locomotion is used by gibbons and siamangs, for example. Brachiator upper limbs are particularly long and strong. Their wrist and shoulder joints are also mobile. This type of locomotion enables them to move very quickly through the canopy – up to 56 km/h for gibbons!

Quadrupedalism

As mentioned at the start of this article, there are three main modes of quadrupedalism: general arboreal quadrupeds, semi-terrestrial quadrupeds and terrestrial quadrupeds. They are all characterized by walking on all four limbs, supported by hands and feet. Quadrupeds can be digitigrades (supported by the toes of the hands and feet), semi-plantigrades, plantigrades (supported by the palms of the hands and feet) or a mixture of both! Baboons, for example, are digitigrade for their hands, but semi-plantigrade for their feet.

The distinction between these modes of quadrupedal locomotion depends on the environment in which they are practiced. Generalist arboreal quadrupeds, such as sakis and cercopithecines, move by walking or running on branches. Semi-terrestrial quadrupeds spend a variable proportion of their time in trees, and come down to the ground to feed. Macaques in general are a good example. Finally, terrestrial quadrupeds live mainly on the ground. Baboons are a case in point.

Quadrupedal locomotion on the knuckles of the hands or knuckle-walking

Knuckle-walking is a form of locomotion that involves moving around on all four limbs, supported by the backs of the phalanges on the upper limbs. This type of movement is practiced by chimpanzees, bonobos and gorillas, for example. This requires adaptations to the bone structure of the wrist and metacarpals, which are more elongated and robust.

We hope you enjoyed this article! Feel free to ask us questions and give us feedback on the blog. You can also contact us by email. You can also follow us on Instagram, Facebook, Twitter, TikTok, LinkedIn and YouTube!

We would like to thank François Druelle, a research fellow specializing in primatology, for his review of the first version of this article.

See you soon,

The Prehistory Travel team.

Bibliography:

[1] Berillon G., Marchal F., “Les multiples bipédies des hominidés”, Pour la Science, vol. 330, 2005.

[2] Grimaud-Hervé et al, Ancestor stories. The great adventure of prehistoryed. Errances,^5th edition, 2015.

[3] Kimura, “Habitual locomotor types and the shape of lower leg bones in primates, especially in hominoids”, Revue de primatology [en ligne], 12|2021.

[4] Michilsens et al, “Functional anatomy of the gibbon forelimb: adaptations to a brachiating lifestyle”, J Anat, 2009 Sep; 215(3): 335-354.

[5] Rasmussen et al, “Tarsier-like locomotor specializations in the Oligocene primate Afrotarsius”, Proc. Natl. Acad. Sci. USA, vol. 95, 1998

[6] Springer C., Andrews P., The complete world of Human evolution, ed. Thames & Hudson, 2011

[7] Tarrega-Saunders et al, “Knuckle-walking and behavioural flexibility in great apes”, Revue de primatology [en ligne], 12|2021

What is a primate? When did these first appear?

The primate order

Primates are an order within the mammal class and the animal kingdom. This order was created in 1758 by Linné in the ^10th edition of his Systema naturae.

As mammals, primates are iteroparous, meaning they can reproduce several times during their lifetime. Primates also have a specific growth pattern that stops once they reach sexual maturity. Like mammals, primates are a senescent species. Individual mortality rates increase with age. Finally, mammals are animals with chromosomal sex determination.

The order Primates includes over 500 species of primates, divided into 12 or 13 families. Primates are found all over the world, but with the exception ofHomo sapiens, Macaca sylvanus in Gibraltar and Macaca fuscata in Japan, they are restricted to tropical and subtropical zones, in forest environments or environments with both savannahs and steppes. Primate species are extremely diverse. Some are diurnal, while others are nocturnal. The smallest primate species weighs 30 grams (Madagascar microcebe), while gorillas can weigh up to 250 kilograms. Most primates are arboreal, although some species, such as macaques, are semi-terrestrial. The definition and classification of primates still raises questions due to the great morphological diversity within this order.

What are the characteristics of primates?

Primates share many common characteristics. Here are just a few examples:

• The volume of the olfactory organs is smaller than the cranial volume
• The orbits are positioned on the front of the face, enabling stereoscopic vision, i.e. 3D vision.
• An upright posture of the trunk in the seated position, which frees up the hands
• Feet have opposable thumbs (with the exception ofHomo sapiens , whose big toe is aligned with the rest of the foot, but this is the product of recent evolution).
• Five fingers on each hand
• At least the first finger has a flat nail instead of a claw
• Absence of a third incisor: 2 incisors per hemi-mandible
• A brain that is relatively larger than the body’s proportions

Nevertheless, the various subdivisions within the primates each have their own morphological characteristics.

When did they appear?

The first true primates, called Euprimates, appeared, according to our current knowledge, around 55 million years ago (later abbreviated to Ma). These Euprimates are classified into two groups: Adapiformes and Omomyiformes. Their geographical origin is a matter of debate. Nevertheless, fossil species have been found in North America, Eurasia and on the Arab-African continent.

These primates are classified into two suborders: Strepsirrhiniens and Haplorhiniens. The Adapiformes share a number of derived characters with the Strepsirrhiniens, enabling them to be grouped together in this clade. The relationship of the Omomyiformes to the Haplorhiniens is less clear, as they do not possess the characters derived from the latter. This difference in classification is based on the structure of these primates’ faces. If we disregard the fossil groups (Adapiformes and Omomyiformes), here are some features to understand the Strepsirrhiniens and Haplorhiniens dichotomy.

Most Euprimata species disappeared around 34 Ma at the time of a major climatic crisis known as the “Great Divide”. This crisis was survived by the Simiiformes, the first apes proper, which appeared during the Eocene either alongside the Adapiformes and Omomyiformes, or as offspring of one or the other.

Around 33 Ma, the Simiiformes split into two new groups: the Platyrrhines and the Catarrhines. Platyrrhines, nicknamed “New World monkeys”, are exclusively American. They have a prehensile tail and 36 teeth (3 premolars per hemi-mandible). “Platyrrhinian” means “flat-nosed” and, indeed, these monkeys have the peculiarity of their nostrils being spread apart and facing outwards. Catarrhinians, also known as “Old World monkeys”, have nostrils that are close together and point downwards. Their dentition consists of 32 teeth (2 premolars per hemi-mandible). A new subdivision within the Catarrhinians occurred around 24-20 Ma. This division separates the Cercopithecoidea and Hominoidea. The former correspond, for example, to macaques or baboons and are characterized by pronogrady, i.e. a tilted trunk. In contrast, the Hominoidea, to which Homo sapiens belongs, are orthograde, i.e. their trunks are upright. The Hominoidea group includes Man and his closest relatives, the chimpanzee, bonobo, gorilla, orangutan, gibbon and siamang. These species are divided into the following families: Hylobatidae, Pongidae and Hominidae(Homo sapiens).

As you can see, Homo sapiens is a primate and an ape like any other! Homo sapiens is the only primate species without an opposable thumb on its foot! We hope you now know each other a little better!

Feel free to ask us questions and give us feedback on the blog. You can also contact us by e-mail. You can also follow us on Instagram, Facebook, TikTok, LinkedIn and Twitter!

See you soon,

The Prehistory Travel team.

Bibliography :

[1] Dominique Grimaud-Hervé et al., Histoire d’ancêtres. La grande aventure de la Préhistoire, Errances, 5^e édition, 2015.

[2] C. F. Ross, R.D Martin, “The role of vision in the Origin and Evolution of Primates, In book: Evolution of Nervous Systems, Publisher: Academic Press, 2007.

[3] Chris Springer, Peter Andrews, The complete world of Human Evolution, Thames & Hudson Ltd Revised edition, 2011.