Hominoids

In hominoids (human and nonhuman apes), the density of spindle cells in the ACC increases with decreasing phylogenetic distance to humans, and the volume of the spindle cell soma correlates positively with relative brain size (Fig. 3), such that humans have the greatest number and volume of spindle neurons, followed past bonobos and chimpanzees (Allman et al., 2002).

From: Evolution of Nervous Systems (Second Edition) , 2017

The Nervous Systems of Non-Human Primates

J.G. Fleagle , Eastward.R. Seiffert , in Evolution of Nervous Systems (Second Edition), 2017

3.01.5.eight Hominoids

Hominoids, apes and humans, are one of the least diverse clades of living primates, but have a very all-encompassing fossil record that begins in the late Oligocene ( Stevens et al., 2013) and that includes many extinct genera in Africa, Europe, and Asia (Fleagle, 2013). There are eight extant hominoid genera and 26 species (about of which are gibbons). Living hominoids are unremarkably divided into three families: Hylobatidae (gibbons), Pongidae (orangutans), and Hominidae (gorillas, chimpanzees, and humans). Although the superfamily originated in Africa, their evolution took place throughout Africa and Eurasia. Just humans accept expanded to other continents. There are numerous genera of stalk hominoids and stem hominids in the fossil record from the tardily Oligocene through Miocene. There are Asian fossils from the Miocene and later that are related to orangutans (Pongo), but at that place are few, if any, identifiable fossil gibbons not attributable to extant taxa (Jablonski and Chapman, 2009), or fossil relatives of the African ape genera, Pan and Gorilla. In contrast, at that place are numerous genera and species of extinct humans (subfamily Homininae).

Compared to other primates, living hominoids are medium to very large in size (v–175   kg). Gibbons are totally arboreal and suspensory, but other hominoids, while more suspensory than most other primates, evidence varying amounts of terrestrial locomotion. Living hominoids include predominantly frugivorous as well as predominantly folivorous taxa; humans are the almost faunivorous/carnivorous hominoids, and our dietary behavior is greatly augmented by cooking and other cultural habits. Bang-up apes (merely non gibbons) show varying amounts of tool use and other cultural abilities. All hominoids take relatively larger brains than other primates, and human brains are among the largest, relative to torso mass, in the animal kingdom (Fig. four). As with other catarrhines, hominoids take routine trichromatic vision and a very reduced or absent-minded vomeronasal organ.

There are 19 species of gibbons (family Hylobatidae) placed in four genera (Hylobates, Symphalangus, Hoolock, and Nomascus), all from tropical parts of Asia. They are medium-sized primates (v–12   kg), totally arboreal and suspensory, with diets that include varying proportions of fruits (peculiarly figs), leaves, and invertebrates. Their rapid brachiating locomotor abilities would seem to require exceptional agility and coordination (Fig. 18). There are no descriptions of tool employ or other cultural behaviors by gibbons.

Effigy 18. Two hylobatids from Malaysia, the white-handed gibbon Hylobates lar (upper left), and the siamang, Symphalangus syndactylus (below).

 Cartoon past Stephen Nash. From Fleagle, J.G., 2013. Primate Adaptation and Development, tertiary ed. Academic Press, New York.

The two species of Orangutans (Pongo) in the family unit Pongidae are from the islands of Borneo and Sumatra, simply there are remains of fossil pongids from many parts of eastern and southeastern Asia.

Hominids are an African radiation. There are two species of gorillas (Fig. 19) and two species of chimpanzees with numerous subspecies of Pan troglodytes. Chimpanzees and humans share many anatomical and behavioral features, including tool utilise and cultural traditions (Fig. xx; Matsuzawa et al., 2011; Whiten et al., 1999).

Figure xix. A group of mountain gorillas Gorilla beringei, in the Virunga volcanoes of Rwanda.

 Drawing past Stephen Nash. From Fleagle, J.Chiliad., 2013. Primate Accommodation and Evolution, 3rd ed. Academic Press, New York.

Effigy 20. A young chimpanzee watches its mother utilize a rock tool.

 Photo provided by Tetsuro Matsuzawa, Kyoto University.

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Apes and Humans

John G. Fleagle , in Primate Adaptation and Evolution (Third Edition), 2013

Abstruse:

Living hominoids (apes and humans), like Old World monkeys, are catarrhine primates. Living apes are characterized past many specializations of how the postcranial skeleton relates to suspensory behavior. All are woods dwellers.They are divided into two families. The hylobatids, or lesser apes, are the gibbons and siamangs of Asia. They are frugivorous and folivorous and travel past brachiation, or arm swinging. They generally live in small-scale monogamous groups. Hominids are the not bad apes and humans. The Asian orangutana are primarily frugivorous, mostly arboreal, and very suspensory. Adults are solitary foragers. The African bang-up apes, gorillas, chimpanzees, and bonobos are found both in the copse and on the ground where they movement by knuckle-walking. Gorillas are largely folivorous while chimps and bonobos are more frugivorous. All alive in large groups, but have different social structures. Humans are very unusual primates and are found on all continents except Antarctica. We accept very large brains, small teeth and reduced body hair. We have easily with a relatively long pollex and dandy manipulative abilities enabling all-encompassing apply of tools of many sorts. Our legs are relatively long and our anxiety have short toes with an adducted hallux. These features enable our bipedal locomotion, both walking and running. Human diets are very diverse and differ from those of other primates in that homo food is often prepared past cooking. Humans live in a broad range of social structures, just all are characterized past extensive prosocial behavior with many adults involved in the raising of offspring. We have the slowest maturation and the longest lifespans of any primate, including long postreprodutive lives among man females.

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Sense Organs and Viscera

Friderun Ankel-Simons , in Primate Anatomy (Third Edition), 2007

THE Large INTESTINE

All hominoid primates have a big intestine that is relatively shorter than it is in monkeys. Moreover, there are no loops in the transverse portion. Both ascending and descending branches are closely attached dorsally to the intestinal wall. A blind ending extension of the upper colon protrudes out from the junction between the small intestine and the colon. This airtight bag has the same diameter every bit the colon and is called a caecum; it is found in all primates. The caecum can often be hook-shaped or fifty-fifty exist slightly spiral-shaped and is frequently haustrated (Langer and Takács, 2004).

The large intestine or colon has mainly excretory functions; information technology also shows certain interesting differences among primates. The large intestine appears less probable to be influenced by functional differences than the modest intestine. However, it is uniquely variable, being smooth, haustrated, short, or long among primates according to their diet. In tarsiers the colon is very simple, and a brusk transverse branch is plant before the colon turns straight downward. The caecum of tarsiers is about equal in length to the large intestine, and the latter lacks whatever flexures or coils. Microcebus and Cheirogaleus accept a colon that resembles that of tarsiers. Among Lemuridae and Lorisidae the colon is long and coiled into a number of corkscrew-like spirals or ansa coli (ansa is Latin for "loop"). The colon is especially long and arranged in a spiral in both Propithecus and Indri, possibly because in these 2 genera the colon is comparatively very long and thus a circular arrangement uses the available space nearly efficiently (Figure 9.23). Also, the round arrangement might prevent the possibility of colon kinks, which would dangerously block the progression of the digesta (from Latin: digestum: "that which has been ingested") in the large tube.

Figure nine.23. The very long large intestine (colon) of Propithecus, which are obligatory leaf-eaters, is arranged in ii discs: the visible disc covers a second colon disc that is thus invisible.

In most Old and New World monkeys the connectedness between ileum and colon is positioned deep caudally at the right side of the abdomen. As the colon ascends from there, it extends across the abdomen above and descends at the left side. A loftier variability of colon configurations has been found among individuals of the New World monkey Saimiri. Onetime and New World monkeys often have loops in the transverse co-operative of the large intestine. The ascending portion of the intestine is closely attached to the dorsal abdominal wall. The big intestine has various dimensions in accordance with the general digestive specialization of various kinds of nonhuman primates. An additional blind-ending extension from the end of the caecum with a much smaller diameter is called the appendix vermiformis (Latin for "worm-shaped appendage"). This "truthful appendix" contains lymphatic tissue, the function of which is not quite understood. The appendix vermiformis is plant in all Hominoidea. Information technology tin can become inflamed in humans, requiring surgery (appendectomy) or, if not diagnosed in a timely fashion, can cause death.

The intestine terminates in the short rectum that leads to the anal opening. The anal opening is regulated past a stiff sphincter muscle.

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Primates

C.C. Sherwood , P.R. Hof , in Evolution of Nervous Systems, 2007

4.21.2.1 Topology of Cortical Maps

Full brain weight in hominoids ranges from approximately 90  g in Kloss's gibbons (Hylobates klossii) to 1400   chiliad in humans (Homo sapiens) (Table ane). While there is a large range of variation among hominoids in full brain size, mapping studies of the cortex (Effigy two) more often than not hold that the location of the chief sensory and motor areas are similar across species (Grünbaum and Sherrington, 1903; Campbell, 1905; Mauss, 1908, 1911; Brodmann, 1909; Leyton and Sherrington, 1917; Beck, 1929; Bailey et al., 1950; Preuss et al., 1999; Hackett et al., 2001; Bush and Allman, 2004a, 2004b; Sherwood et al., 2004b). In detail, the primary visual cortex lies within the banks of the calcarine sulcus. Primary auditory cortex is located on the posterior superior airplane of the superior temporal gyrus, usually comprising the transverse gyrus of Heschl in corking apes and humans. Primary somatosensory cortex is establish within the posterior banking concern of the key sulcus and extends on to the postcentral gyrus. Primary motor cortex is located mostly on the inductive bank of the central sulcus. One notable difference is the fact that master visual cortex extends to only a very pocket-sized portion of the lateral convexity of the occipital lobe in humans, whereas a much larger part of the lateral occipital lobe is comprised of striate cortex in apes (Zilles and Rehkämper, 1988; Holloway et al., 2003). This is because the primary visual cortex in humans is 121% smaller than expected for a primate of the same brain size (Holloway, 1996). Other higher-order areas, peculiarly within the frontal cortex, take likewise been shown to occupy similar locations across these species (Strasburger, 1937a, 1937b; Semendeferi et al., 1998, 2001; Sherwood et al., 2003a).

Table one. Endocranial volumes of hominoids (in cc)

Common name Species Sex Sample size Hateful SD Range
White-handed gibbon Hylobates lar K 44 106.iii 7.2 92–125
F 37 104.two 7.0 90–116
Siamang Symphalangus syndactylus M viii 127.seven 8.2 99–140
F 12 125.9 12.vii 102–143
Orangutan Pongo pygmaeus M 66 415.6 33.half dozen 334–502
F 63 343.one 33.6 276–431
Gorilla Gorilla gorilla 1000 283 535.five 55.three 410–715
F 199 452.2 41.6 345–553
Chimpanzee Pan troglodytes Thousand 159 397.ii 39.4 322–503
F 204 365.7 31.9 270–450
Bonobo Pan paniscus M 28 351.8 thirty.six 295–440
F xxx 349.0 37.7 265–420
Human Human being sapiens M 502 1457.2 119.8 1160–1850
F 165 1317.9 109.8 1040–1615

Endocranial volumes are shown, rather than encephalon volumes, because larger sample sizes are available for these species. Reproduced from Holloway, R. Fifty. 1996. Evolution of the human being brain. In: Handbook of Human Symbolic Evolution (eds. A. Lock and C. R. Peters), pp. 74–114. Oxford University Press.

Figure 2. Parcellation maps of the cognitive cortex of apes. Chimpanzee (Pan troglodytes) cortical maps reproduced from (a) Campbell, A. W. 1905. Histological Studies on the Localisation of Cognitive Function. Cambridge University Printing. and (b) Bailey, P., von Bonin, K., and McCulloch, W. S. 1950. The Isocortex of the Chimpanzee. University of Illinois Press. Orangutan (Pongo pygmaeus) cortical maps reproduced from (c) Campbell (1905) and (d) Mauss (1908, 1911) compiled in Zilles and Rekämper (1988). c and d, Reproduced from "figure 12-2", Orang-utan Biology, edited by Jeffrey H. Schwartz, copyright © 1988 past Oxford University Press, Inc., used by permission of Oxford Academy Press, Inc.

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Evolution of the Primate Brain

Chet C. Sherwood , ... Patrick R. Hof , in Progress in Brain Inquiry, 2012

The emergence of neuronal specializations for social noesis: VENs

Another interesting feature of the hominoid cerebral cortex is the presence of VENs (Fig. 4; Allman et al., 2010; Nimchinsky et al., 1995, 1999; Seeley et al., 2012; von Economo, 1926). VENs are projection neurons located principally in layer V of the anterior cingulate and frontoinsular cortices and, in more than limited numbers, in the superior frontal cortex (area 9; Fajardo et al., 2008). Current information suggest that VENs represent a specialized neuronal blazon with a feature morphology that evolved merely in a restricted number of species, most likely from a population of pyramidal neurons present in ancestral mammals (Butti and Hof, 2010; Butti et al., 2011). VENs, which are particularly numerous in the hominoid lineage, are particularly vulnerable in neuropsychiatric weather in which social and emotional skills are characteristically affected. Moreover, contempo bear witness on the neurochemical contour, morphologic features, and laminar and regional distribution of VENs suggests that the functional specificity of this neuronal population could exist critically involved in autonomic regulation.

Fig. 4. von Economo neurons (VENs) as revealed past Nissl staining from layer V of anterior cingulate cortex in great apes and humans. (a) human, (b) chimpanzee, (c) bonobo, and (d) gorilla. Scale bar   =   100   μm.

VENs are by and large larger than layer Five pyramidal neurons and their somatic volume is strongly correlated with the encephalization quotient, unlike that of pyramidal cells (Nimchinsky et al., 1999). In adults, VENs are more arable in the right hemisphere (Allman et al., 2010), peradventure reflecting asymmetries in the organization of afferents from the autonomic nervous system (Craig, 2005). Their densities, however, are low in all species in which they occur, representing but a few percent of the total number of pyramidal neurons (Allman et al., 2010). VENs have been shown to be enriched in nonphosphorylated epitopes of neurofilament proteins, like to large pyramidal neurons (Nimchinsky et al., 1995), and to express several markers such equally dopamine D3 receptor, vasopressin 1a receptor, activating transcription factor 3, interleukin-four receptor α concatenation, neuromedin B, gastrin-releasing peptide, and disrupted on schizophrenia-1, in higher levels than neighboring pyramidal cells (Allman et al., 2010, 2011; Stimpson et al., 2011).

The function of VENs remains poorly understood. Nonetheless, it is interesting that VENs are afflicted in a number of neuropsychiatric illnesses that present impairments of social and advice skills, emotionality, morality, and self-sensation. They are severely lost in the behavioral variant of frontotemporal dementia and in agenesis of the corpus callosum (Kaufman et al., 2008; Kim et al., 2012; Seeley et al., 2006), showroom decreased densities in schizophrenia (Brüne et al., 2010), and show abnormal cortical distribution and increased number in young children with autism (Santos et al., 2011), every bit well as increased densities in suicide victims with psychosis (Brüne et al., 2011). The specific localization of VENs in cortical areas in which information on the physiological state of the body is used to guide behavioral choices (Craig, 2009), their involvement in diseases in which social conduct is dramatically afflicted, their richness in markers such as bombesin-related peptides, and their position in a layer characteristically sending subcortical projections (Brodal, 1978; Glickstein et al., 1985) suggest a part for VENs in cortico-autonomic pathways, supporting the original intuition of von Economo (1926) on the involvement of VENs in autonomic function. The fact that they have too independently emerged in other big-brained social mammals, such as elephants and whales (Butti et al., 2009; Hakeem et al., 2009; Hof and Van der Gucht, 2007), strongly suggests that their development is mediated by mechanisms related to brain size scaling.

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Retrotransposons of Vertebrates

A.E. Peaston , in Encyclopedia of Virology (Third Edition), 2008

SVA structure

SVA elements, exclusively found in hominoid primates, are chimeric elements named for their principal components, SINE-R, VNTR, and Alu. A v′ (CCCTCT) hexamer repeat is followed past an antisense Alu sequence and and then, multiple copies of a variable number tandem repeat (VNTR). The 3′ portion consists of the primate-specific SINE-R, derived from an LTR-retrotransposon thought to be human endogenous retrovirus K-ten (HERVK-10), and finally a polyadenylation and cleavage signal and poly (A) tail.

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The Nervous Systems of Non-Human Primates

S. Almécija , C.C. Sherwood , in Evolution of Nervous Systems (2nd Edition), 2017

3.xvi.6.ane Manus Evolution

As previously mentioned, compared to other hominoids, modernistic humans display especially dexterous hands facilitated by a unique type of interaction between the proximal pulps of our thumb and fingers ( Napier, 1962; Fig. 2). Previous analyses of hand bone morphology in Plio-Pleistocene australopiths (Alba et al., 2003; Green and Gordon, 2008; Moyà-Solà et al., 2008; Kivell et al., 2011; Almécija and Alba, 2014) and the Miocene hominin Orrorin (Gommery and Senut, 2006; Almécija et al., 2010) provide compelling bear witness that humanlike precision grasping (every bit inferred from a humanlike bony morphology) preceded the widespread use of flaked stone tools, which supports the idea that modernistic humans exhibit the plesiomorphic condition for hand digit length ratios (Fig. 4B). The emerging evolutionary moving-picture show is that increased reliance on bipedalism and enhanced manipulation were very early specializations of the hominin lineage, as a part of an initial adaptive shift from apes in relation to new foraging strategies, simply they were not necessarily specifically related to rock tool civilization (Hunt, 1994; Alba et al., 2003; Almécija et al., 2010; Almécija and Alba, 2014). While overall australopiths combined a complex mosaic of apelike and humanlike features (Fig. 1B), in terms of hand proportions, these early hominins appear more than like to modern humans than to suspensory living apes', and thus likely had comparable musculoskeletal capabilities for humanlike manipulation (Alba et al., 2003; Green and Gordon, 2008; Almécija et al., 2010; Kivell et al., 2011; Almécija and Alba, 2014). Still, this does not necessarily mean that man easily evolved for the sole purpose of making and using rock tools, which would have required parallel changes in cognitive capabilities (Napier, 1962). In other words, the eventual application of humanlike manus structure to stone tool flaking and use was virtually certainly an "exaptation" (sensu Gould and Vrba, 1982), non an accommodation (Alba et al., 2003).

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Molecular Clock

West.-H. Li , K. Makova , in Encyclopedia of Genetics, 2001

Lower Rates in Humans than in Monkeys

In that location has been a longstanding controversy over the hominoid rate-slowdown hypothesis, which postulates that the rate of molecular evolution has become slower in hominoids (humans and apes) later on their separation from the Quondam World (OW) monkeys. This hypothesis, proposed by Goodman (1961) and Goodman et al., (1971), was based on rates estimated from immunological distance and protein sequence data. Wilson et al. (1977) contended that the slowdown was an artifact, attributable to the apply of an erroneous paleontological estimate of the ape–human divergence time. They conducted relative-rate tests using both immunological distance information and poly peptide sequence data and concluded that at that place was no testify for a hominoid slowdown. However, comparative analyses of Dna sequence information by Koop et al., (1986), Li and Tanimura, (1987), and others provided stiff support for the hominoid slowdown hypothesis and the hypothesis was accustomed by many molecular evolutionists.

Table two shows some comparisons of the substitution rates in the human and OW monkey lineages. In the table, Thou 13 and Grand 23 are the distances betwixt an OW monkey and a New World (NW) monkey and betwixt the human being and a NW monkey, respectively. For the introns compared Yard 13 − K 23 is positive, except that K 13 − K 23 is 0 for the ε-globin and interferon-α receptor introns and is slightly negative for the lipoprotein lipase intron. When all introns are considered together K thirteen − K 23 is significantly greater than 0, implying that the rate in the OW monkey lineage is significantly faster than that in the homo lineage. The same determination is obtained from the flanking sequence data (Table two). Thus, at that place is indeed prove for the hominoid-slowdown hypothesis.

Table two. Differences in the number of nucleotide substitutions per 100 sites and the relative rates of substitution between the Old World monkey (species i) and human being (species 2) lineages, with the New World monkey (species 3) as a reference

Sequence Nucleotides compared K 12 a One thousand 13 a M 23 a Chiliad 13 − M 23 Rate ratio b
η-globin pseudogene c 8,781 six.7 11.viii 10.vii 1.1 ± 0.three** 1.4
Introns
  IGF2 ane,589 6.four 15.viii 14.2 1.6 ± 0.viii* 1.7
  ɛ-globin 928 4.9 11.five 11.v 0.0 ± 0.viii 1.0
  Insulin 862 9.7 17.0 fifteen.9 i.ane ± ane.3 1.3
  Mast-cell carboxypeptide 1,275 5.v 13.3 12.5 0.8 ± 0.8 1.3
  Carbonic anhydrase seven 501 7.2 11.1 9.7 i.5 ± 1.4 1.5
  Interferon-α receptor 885 7.6 fourteen.0 fourteen.0 0.0 ± one.1 1.0
  Apolipoprotein C3 ane,270 viii.7 18.five sixteen.9 ane.vi ± ane.0 ane.5
  Lipoprotein lipase ane,168 vii.nine 13.half-dozen 13.eight −0.three ± 1.0 1.0
  Total 8,478 seven.1 14.7 13.9 0.eight ± 0.3** 1.three
Flanking and untranslated regions
  ɛ-globin 388 5.three 13.5 10.six 2.9 ± i.iv* 3.4
  Insulin 548 9.eight 15.viii 12.6 3.two ± 1.5* 2.0
  Full 936 7.ix xiv.9 11.7 3.i ± one.1** 2.3

Data from Bailey et al. (1991), Porter et al. (1995), and Ellsworth et al. (1993 and unpublished).

a
K ij = number of substitutions per 100 sites between species i and j.
a
The ratio of the rate in the Old World monkey lineage to the rate in the human lineage.
c
Excluding Alu sequences.
*
Pregnant at the 5% level.
**
Pregnant at the 1% level.

The intron sequence data advise that the OW monkey lineage evolves i.three times faster than the homo lineage, which is similar to that (1.4) estimated from the -globin data. The flanking sequence data advise that the rate ratio is more 2 times. Even so, since the latter information set is small, the ratio estimated from this set up may not exist reliable. Farther data are needed to see whether the ratio varies among unlike DNA regions.

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Primitive Catarrhines and Fossil Apes

John G. Fleagle , in Primate Accommodation and Evolution (Third Edition), 2013

Evolution of Gibbons

In each of the successive radiations of Oligocene and Miocene hominoids there have been minor apes that, at one fourth dimension or another have been identified as fossil gibbons. Propliopithecus, Pliopithecus, Epipliopithecus, Dendropithecus, Micropithecus, and Dionysopithecus all prove diverse features (such as pocket-sized size, short snouts, or large orbits) that cause them to resemble living lesser apes. As already discussed, however, most of these supposed fossil gibbons were extremely archaic in many detailed aspects of their cranial and skeletal anatomy, more than then than we would expect in an ancestral gibbon based on the comparative anatomy of extant higher primates. For example, although Propliopithecus and Pliopithecus were similar to living gibbons in their size and (in some species) had simple, superficially gibbon-like lower molars, they lacked such features equally the tubular ectotympanic os found in all living apes and One-time World monkeys, and they retained primitive features in their limb bones that are lacking in the limbs of all living catarrhines. For other genera, such as Micropithecus, Dendropithecus, and Laccopithecus, at that place are suggestive cranial remains, although critical information almost the ear region, and particularly the limb skeleton, is not available, but they testify other features that link them with other more primitive taxa. Merely the poorly known Yuanmoupithecus from the Belatedly Miocene of China seems to exist a feasible candidate to be a real fossil gibbon.

All of the small apes from Africa and Eurasia were probably to some extent ecological vicars of the living bottom apes, simply there is no existent indication of a gibbon lineage prior to the last 8 one thousand thousand years (Harrison et al., 2008). Nonetheless, molecular estimates of the date of the divergence of gibbons from the hominoid lineage suggest an origin of the lineage leading to the lesser apes near 20 million years agone (eastward.yard., Perelman et al., 2011). This fourth dimension range includes that of virtually all of the primitive catarrhines from the Early Miocene of Africa, besides as the fossil apes from Europe, that seem to mark the appearance of the bang-up ape and man clade, which must accept been casual with the origin of the gibbon lineage. The absence of any evidence of a gibbon lineage throughout much of the Miocene is a major gap in our agreement of primate evolution that raises many unanswered questions. Are the similarities between gibbons and other hominoids the issue of extensive homoplasy, and gibbons are derived from one of the archaic catarrhines from the Miocene of Africa or Eurasia? Is the modest size of extant gibbons a contempo phenomenon, such that some of the primitive 'great apes' of Europe are really early on hylobatids? Or was hylobatid evolution a small, regional phenomenon that took place outside the parts of the globe with a fossil tape?

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Primates

T.M. Preuss , in Evolution of Nervous Systems, 2007

The order Primates is the grouping of mammals that includes the hominoids (apes and humans), Erstwhile Globe monkeys, New Earth monkeys, tarsiers, lemurs, lorises, and bush babies. Enormous progress has been made over the past three decades in understanding the relationships of primates to other mammals, the relationships amidst primate groups, and the adaptive origins of primates and of primate subgroups. Several lines of show point that primates vest to a higher-order grouping of mammals, the Archonta, that includes at to the lowest degree tree shrews and flying lemurs. Primates probably originated every bit a group of small, nocturnally agile animals, evolving grasping extremities and close-set, forward-facing eyes to locomote and feed in the fine last branches of tree. The origin of anthropoid primates (New Earth monkeys, Sometime World monkeys, and hominoids) was marked by a shift to diurnality and the development of a retinal fovea for enhanced visual acuity, followed by increased trunk size and the advent of more circuitous forms of social organization Primate brain development was marked by changes at many levels of structural organization. Brain size increased early on in primate development, with expansion of the neocortex and the addition of numerous new cortical sensory areas and new systems of interconnections betwixt areas. Also, primates evolved new areas in higher-gild cortical regions such as posterior parietal, superior temporal sulcal, and dorsolateral prefrontal cortex, and a new thalamic nucleus, the dorsal (medial) pulvinar, which has extensive connections with the higher-guild cortex. The evolution of anthropoid primates was accompanied by farther increases in brain size, and the appearance of new areas, especially in higher-order and limbic regions, although it is not clear that the addition of new areas accounts for the increased encephalization of anthropoids. Evolutionary changes in primate brain organization were past no ways limited to changes in the complement of areas and extrinsic connectivity: numerous changes in the internal laminar and modular system of cortical areas have been documented, and there is increasing show of changes in the morphological and biochemical phenotypes of encephalon cells.

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