Chimpanzee Evolution: Difference between revisions

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==Behavioral Adaptations==
==Behavioral Adaptations==
Behavior in chimpanzees, much like that of other primates, is thought to be the variable result of a combination of genetics and the environment.<ref>[https://www.journals.uchicago.edu/doi/full/10.1086/692830?casa_token=R0ZXc6lPWhEAAAAA%3AGreKFpvpAtuBDHEeocuZxI-Z6h-sgLJ_RvYM5dVEP20vKY2gTeY1gzLIRhw8oldCtk7GnSIH2ko Greene HW. Evolutionary scenarios and primate natural history. Am Nat. 2017;190(august):S69–86.]</ref> Chimpanzee behavior, therefore, varies, often in accordance with population; each population exhibits broad behavioral patterns, ranging from rain dances to use of levers (Fig. 4).<ref>[https://www.nature.com/articles/21415 Palaeontographica VA, Das P, Whiten  a, Goodall J, Mcgrew WC, Nishida T, et al. Cultures in chimpanzees troglodytes ) have achieved long-term status across Africa , differ- lated 151 years of chimpanzee observation . This comprehensive analysis reveals patterns of variation that are far more extensive than have previously been docume. Nature. 1999;399(JUNE):15–8.]</ref>
Behavior in chimpanzees, much like that of other primates, is thought to be the variable result of a combination of genetics and the environment.<ref>[https://www.journals.uchicago.edu/doi/full/10.1086/692830?casa_token=R0ZXc6lPWhEAAAAA%3AGreKFpvpAtuBDHEeocuZxI-Z6h-sgLJ_RvYM5dVEP20vKY2gTeY1gzLIRhw8oldCtk7GnSIH2ko Greene HW. Evolutionary scenarios and primate natural history. Am Nat. 2017;190(august):S69–86.]</ref> Chimpanzee behavior, therefore, varies, often in accordance with population; each population exhibits broad behavioral patterns, ranging from rain dances to use of levers (Fig. 4).<ref>[https://www.nature.com/articles/21415 Palaeontographica VA, Das P, Whiten  a, Goodall J, Mcgrew WC, Nishida T, et al. Cultures in chimpanzees troglodytes ) have achieved long-term status across Africa , differ- lated 151 years of chimpanzee observation . This comprehensive analysis reveals patterns of variation that are far more extensive than have previously been docume. Nature. 1999;399(JUNE):15–8.]</ref>
[[Image:Whiten et al fig.1.png|thumb|300px|left|Fig. 4: Distribution of behavior patterns in chimpanzees across six African study sites. Color icons, customary; circular icons, habitual; monochrome icons, present; clear, absent; horizontal bar, absent with ecological explanation; question mark, answer uncertain. Published in June 1999 in Nature; Whiten et al "Cultures in Chimpanzees" [https://www.nature.com/articles/21415].]]
[[Image:Whiten et al fig.1.png|thumb|200px|left|Fig. 4: Distribution of behavior patterns in chimpanzees across six African study sites. Color icons, customary; circular icons, habitual; monochrome icons, present; clear, absent; horizontal bar, absent with ecological explanation; question mark, answer uncertain. Published in June 1999 in Nature; Whiten et al "Cultures in Chimpanzees" [https://www.nature.com/articles/21415].]]
Tool use, in particular, has been studied in chimpanzees.<ref>[https://www.nature.com/articles/21415 Palaeontographica VA, Das P, Whiten  a, Goodall J, Mcgrew WC, Nishida T, et al. Cultures in chimpanzees troglodytes ) have achieved long-term status across Africa , differ- lated 151 years of chimpanzee observation . This comprehensive analysis reveals patterns of variation that are far more extensive than have previously been docume. Nature. 1999;399(JUNE):15–8.]</ref><ref>[https://www.sciencedirect.com/science/article/pii/S0047248417304803?casa_token=PaK4JoV1--oAAAAA:TBKsVlDnY6SD0YxnZg5twyXaodRgUvPyYNNBmGRftl50Dy59Al7DHnbWcpTz9dIzXg9HpjQ0tw Proffitt T, Haslam M, Mercader JF, Boesch C, Luncz L V. Revisiting Panda 100, the first archaeological chimpanzee nut-cracking site. J Hum Evol. 2018;124:117–39.]</ref><ref>[https://www.journals.uchicago.edu/doi/full/10.1086/692830?casa_token=R0ZXc6lPWhEAAAAA%3AGreKFpvpAtuBDHEeocuZxI-Z6h-sgLJ_RvYM5dVEP20vKY2gTeY1gzLIRhw8oldCtk7GnSIH2ko Greene HW. Evolutionary scenarios and primate natural history. Am Nat. 2017;190(august):S69–86.]</ref> The use of percussive tools, most commonly used to crack nuts, is a common example of tool use in chimpanzees and currently the only significant instance of behavioral differentiation between subspecies, as opposed to populations.<ref>[https://www.nature.com/articles/21415 Palaeontographica VA, Das P, Whiten  a, Goodall J, Mcgrew WC, Nishida T, et al. Cultures in chimpanzees troglodytes ) have achieved long-term status across Africa , differ- lated 151 years of chimpanzee observation . This comprehensive analysis reveals patterns of variation that are far more extensive than have previously been docume. Nature. 1999;399(JUNE):15–8.]</ref><ref>[https://www.sciencedirect.com/science/article/pii/S0047248417304803?casa_token=PaK4JoV1--oAAAAA:TBKsVlDnY6SD0YxnZg5twyXaodRgUvPyYNNBmGRftl50Dy59Al7DHnbWcpTz9dIzXg9HpjQ0tw Proffitt T, Haslam M, Mercader JF, Boesch C, Luncz L V. Revisiting Panda 100, the first archaeological chimpanzee nut-cracking site. J Hum Evol. 2018;124:117–39.]</ref> In foraging and hunting, chimpanzees often use probing sticks to collect insects or honey, though specific use varies by population.<ref>[https://www.nature.com/articles/21415 Palaeontographica VA, Das P, Whiten  a, Goodall J, Mcgrew WC, Nishida T, et al. Cultures in chimpanzees troglodytes ) have achieved long-term status across Africa , differ- lated 151 years of chimpanzee observation . This comprehensive analysis reveals patterns of variation that are far more extensive than have previously been docume. Nature. 1999;399(JUNE):15–8.]</ref><ref>[https://www.journals.uchicago.edu/doi/full/10.1086/692830?casa_token=R0ZXc6lPWhEAAAAA%3AGreKFpvpAtuBDHEeocuZxI-Z6h-sgLJ_RvYM5dVEP20vKY2gTeY1gzLIRhw8oldCtk7GnSIH2ko Greene HW. Evolutionary scenarios and primate natural history. Am Nat. 2017;190(august):S69–86.]</ref> In addition,  chimpanzees have been known to fashion spears and lances, made of wood and sharpened with their teeth, to puncture prey (Fig. 5).<ref>[https://www.journals.uchicago.edu/doi/full/10.1086/692830?casa_token=R0ZXc6lPWhEAAAAA%3AGreKFpvpAtuBDHEeocuZxI-Z6h-sgLJ_RvYM5dVEP20vKY2gTeY1gzLIRhw8oldCtk7GnSIH2ko Greene HW. Evolutionary scenarios and primate natural history. Am Nat. 2017;190(august):S69–86.]</ref>
Tool use, in particular, has been studied in chimpanzees.<ref>[https://www.nature.com/articles/21415 Palaeontographica VA, Das P, Whiten  a, Goodall J, Mcgrew WC, Nishida T, et al. Cultures in chimpanzees troglodytes ) have achieved long-term status across Africa , differ- lated 151 years of chimpanzee observation . This comprehensive analysis reveals patterns of variation that are far more extensive than have previously been docume. Nature. 1999;399(JUNE):15–8.]</ref><ref>[https://www.sciencedirect.com/science/article/pii/S0047248417304803?casa_token=PaK4JoV1--oAAAAA:TBKsVlDnY6SD0YxnZg5twyXaodRgUvPyYNNBmGRftl50Dy59Al7DHnbWcpTz9dIzXg9HpjQ0tw Proffitt T, Haslam M, Mercader JF, Boesch C, Luncz L V. Revisiting Panda 100, the first archaeological chimpanzee nut-cracking site. J Hum Evol. 2018;124:117–39.]</ref><ref>[https://www.journals.uchicago.edu/doi/full/10.1086/692830?casa_token=R0ZXc6lPWhEAAAAA%3AGreKFpvpAtuBDHEeocuZxI-Z6h-sgLJ_RvYM5dVEP20vKY2gTeY1gzLIRhw8oldCtk7GnSIH2ko Greene HW. Evolutionary scenarios and primate natural history. Am Nat. 2017;190(august):S69–86.]</ref> The use of percussive tools, most commonly used to crack nuts, is a common example of tool use in chimpanzees and currently the only significant instance of behavioral differentiation between subspecies, as opposed to populations.<ref>[https://www.nature.com/articles/21415 Palaeontographica VA, Das P, Whiten  a, Goodall J, Mcgrew WC, Nishida T, et al. Cultures in chimpanzees troglodytes ) have achieved long-term status across Africa , differ- lated 151 years of chimpanzee observation . This comprehensive analysis reveals patterns of variation that are far more extensive than have previously been docume. Nature. 1999;399(JUNE):15–8.]</ref><ref>[https://www.sciencedirect.com/science/article/pii/S0047248417304803?casa_token=PaK4JoV1--oAAAAA:TBKsVlDnY6SD0YxnZg5twyXaodRgUvPyYNNBmGRftl50Dy59Al7DHnbWcpTz9dIzXg9HpjQ0tw Proffitt T, Haslam M, Mercader JF, Boesch C, Luncz L V. Revisiting Panda 100, the first archaeological chimpanzee nut-cracking site. J Hum Evol. 2018;124:117–39.]</ref> In foraging and hunting, chimpanzees often use probing sticks to collect insects or honey, though specific use varies by population.<ref>[https://www.nature.com/articles/21415 Palaeontographica VA, Das P, Whiten  a, Goodall J, Mcgrew WC, Nishida T, et al. Cultures in chimpanzees troglodytes ) have achieved long-term status across Africa , differ- lated 151 years of chimpanzee observation . This comprehensive analysis reveals patterns of variation that are far more extensive than have previously been docume. Nature. 1999;399(JUNE):15–8.]</ref><ref>[https://www.journals.uchicago.edu/doi/full/10.1086/692830?casa_token=R0ZXc6lPWhEAAAAA%3AGreKFpvpAtuBDHEeocuZxI-Z6h-sgLJ_RvYM5dVEP20vKY2gTeY1gzLIRhw8oldCtk7GnSIH2ko Greene HW. Evolutionary scenarios and primate natural history. Am Nat. 2017;190(august):S69–86.]</ref> In addition,  chimpanzees have been known to fashion spears and lances, made of wood and sharpened with their teeth, to puncture prey (Fig. 5).<ref>[https://www.journals.uchicago.edu/doi/full/10.1086/692830?casa_token=R0ZXc6lPWhEAAAAA%3AGreKFpvpAtuBDHEeocuZxI-Z6h-sgLJ_RvYM5dVEP20vKY2gTeY1gzLIRhw8oldCtk7GnSIH2ko Greene HW. Evolutionary scenarios and primate natural history. Am Nat. 2017;190(august):S69–86.]</ref>
[[Image:Greene fig.3B.png|thumb|200px|right|Fig. 5: Field sample of lances fashioned by chimpanzees for hunting bushbabies in Senegal. Published in H. W. Greene's "Evolutionary Scenarios and Primate Natural History," 2017. Photo credits: J. Pruetz [https://www.journals.uchicago.edu/doi/full/10.1086/692830?casa_token=ZZKhkO3tz8YAAAAA%3A0DX0OjKKEk9zEn_DYMLhTx5eI9LmLeB94Bu6dwIf1JerS3xOOnP0PKaml4q3cYx8wYrcNZHE0YM].]]
[[Image:Greene fig.3B.png|thumb|200px|right|Fig. 5: Field sample of lances fashioned by chimpanzees for hunting bushbabies in Senegal. Published in H. W. Greene's "Evolutionary Scenarios and Primate Natural History," 2017. Photo credits: J. Pruetz [https://www.journals.uchicago.edu/doi/full/10.1086/692830?casa_token=ZZKhkO3tz8YAAAAA%3A0DX0OjKKEk9zEn_DYMLhTx5eI9LmLeB94Bu6dwIf1JerS3xOOnP0PKaml4q3cYx8wYrcNZHE0YM].]]

Revision as of 20:22, 8 December 2020

Introduction and Early Evolution

Pan troglodytes, better known as chimpanzees, are a species of great ape widely regarded as the closest living relatives to bonobos (Pan paniscus) and one of the closest living relatives to humans (Homo sapiens; Fig. 1).[1][2]

Fig. 1: Adult male chimpanzee (Pan troglodytes); photo taken 26 October 2006 in Shanghai Wildlife Park, Shanghai, China. Photographer: David Blank[1].

The evolution of chimpanzees is thought to have begun, like that of many other primates, with the divergence of platyrrhines (also known as New World monkeys) and catarrhines (a group containing Old World monkeys and apes) 25-40 million years ago [3] This was followed by a divergence in the catarrhines, forming the Hominoidea (ape) and Cercopithecoidea (Old World monkey) groups 23 million years ago. [4] It is estimated that the genera Homo and Pan diverged 5-6 million years ago, followed by a split in the genus Pan roughly 2.4 million years ago, eventually culminating into the chimpanzees and bonobos present today (Fig. 2). [5][6] [7][8]

Fig. 2: Phylogenetic relationships and classification of primates. This figure was included in H. W. Greene's "Evolutionary Scenarios and Primate Natural History," published in 2017. [2].

Continuing Evolution and Speciation

Evolution has not stopped with the modern chimpanzee. There are currently four recognized subspecies: the central chimpanzee (P. t. troglodytes), the western chimpanzee (P. t. verus), the eastern chimpanzee (P. t. schweinfurthii), and the Nigeria-Cameroon chimpanzee (P. t. ellioti) (Fig. 3). [9][10][11][12]

The subspecies are geographically isolated by the Sanaga River, which separates the western and Nigeria-Cameroon subspecies from the central and eastern chimpanzees, and the Ubangi River, which is the primary barrier between the latter two subspecies. [13] The Niger River and the Dahomey Gap (a stretch of dry forest across Western Africa) have both been hypothesized as barriers that have separated the western and Nigeria-Cameroon chimpanzees.[14] However, not all of these geographic barriers are complete; researchers have recently recorded migration between eastern and central chimpanzee subspecies.[15][16] Sequencing of mitochondrial DNA has revealed that there are two major chimpanzee lineages; one clade is formed by the central and eastern chimpanzees, while western and Nigeria-Cameroon chimpanzees form the other clade.[17] Subspeciation is further enforced by variable susceptibility to specific viral infections.[18][19]Simian immunodeficiency virus (SIV), the precursor to the human immunodeficiency virus (HIV), is known to infect only P. t. troglodytes and P. t. schweinfurthii.[20][21] Chimpanzee subspecies have also shown specific behavioral differences, most notably that nut-cracking behavior only occurs in the west.[22][23]

Fig. 3: A. The geographic ranges of each chimpanzee subspecies B. Phylogenetic relationships amongst chimpanzees and the timing of their population divergence; 1 kya = long term effective population sizes up to 1kya, present = population sizes 1kya to present. Color designates subspecies; Blue = western, red = Nigeria-Cameroon, green = central, orange = eastern. Published in Schmidt et al "The impact of genetic adaptation on chimpanzee subspecies differentiation," November 2019. [3].

In addition to continuous speciation, chimpanzees face extinction.[24][25] [26] Each subspecies is classified as endangered, the western chimpanzee critically so, having declined by about 80% in 24 years.[27] This population decrease has been attributed to factors including illegal hunting, habitat loss, and infectious diseases; regional extinctions in Burkina Faso and Côte d’Ivoire have reduced the western chimpanzee’s geographic range by 20%.[28]

Distinct Genetic Adaptations

Chimpanzees, living in a variety of environments, are adapted in a variety of ways. The effect of environment is evident in locomotion, suitable for both terrestrial and arboreal settings.[29] Scientists have recorded instances of quadrupedalism and bipedalism in chimpanzee populations; neither type of locomotion is favored over the other in terms of energy efficiency, but locomotion in general has a relatively high metabolic cost in chimpanzees (41% more energy than expected for a mammal of similar body mass)[30] In addition, when bipedal, chimpanzees tend to take relatively small, frequent steps and require more side-to-side motion than habitual bipeds, typical of non-human primates.[31] This may be indicative of the lack of specialized anatomical structures for bipedalism; with a necessity to move effectively in a variety of environments, chimpanzees benefit from different possible types of locomotion.[32][33]

Many of the chimpanzee’s features are studied in relation to its human relatives, particularly concerning a chimpanzee-human last common ancestor and the rise of habitual bipedality.[34][35][36][37] For example, chimpanzees and humans are depicted similarly in the effect of aging on the thoracolumbar region, for which there is a difference seen in the region based on age (as opposed to the thoracolumbar region of gorillas).[38] In further comparison to Homo sapiens, alternative specialization is often studied in chimpanzees as means of characterizing the last common Pan-Homo common ancestor. This is evident in a comparison of muscle strength in the two primates; chimpanzees, on average, display a mass-specific muscular performance 1.5 times greater than humans, which may be similar to that of the last common ancestor between humans and chimpanzees. [39]

Chimpanzees have also developed a distinct microbiome, most notably in the gut, which fluctuates socially and seasonally. [40][41] Chimpanzee gut microbiomes are mostly similar to those of other great apes, with a few key differences. [42] The gut microbiome is largely regulated by diet; because chimpanzees are primarily (though not exclusively) frugivores, their gut microbiome does not fluctuate nearly as much as those of other great apes who might be more seasonal eaters.[43] However, this does not mean that the chimpanzee gut microbiome does not fluctuate seasonally; in a 2018 study, it was noted that chimpanzees were distinguished by the relative abundance of Erysipelotrichaceae taxa, Prevotella, RFN20, and Sphaerochaeta. [44] ). During dry months (May-October), chimpanzees had a considerable amount of Prevotella, while wet months (November-April) were characterized by high levels of Sphaerochaeta. [45][46] This seasonal fluctuation is coupled with social fluctuation.[47] Socially-based microbial development, unlike seasonal fluctuations, affect species richness within individuals, rather than specific bacterial abundance. [48] Chimpanzees display different social patterns in accordance with the season; while dry seasons are usually associated with relative solitude, wet seasons correspond with high sociability.[49] Furthermore, inheritance of gut microbial communities appears to be primarily horizontal, rather than vertically from parent to offspring, suggesting that sociability is necessary to maintain and develop microbial communities in chimpanzees.[50] In this way, chimpanzee populations cultivate microbial communities, in which microbiomes are connected by the interaction of their hosts; microbes have even been known to transfer between the guts of chimpanzees and gorillas.[51][52] ). The combination of seasonal and social fluctuations in the gut microbiome has granted chimpanzees resilience to changes in nutrient availability and disease.[53][54]

Behavioral Adaptations

Behavior in chimpanzees, much like that of other primates, is thought to be the variable result of a combination of genetics and the environment.[55] Chimpanzee behavior, therefore, varies, often in accordance with population; each population exhibits broad behavioral patterns, ranging from rain dances to use of levers (Fig. 4).[56]

Fig. 4: Distribution of behavior patterns in chimpanzees across six African study sites. Color icons, customary; circular icons, habitual; monochrome icons, present; clear, absent; horizontal bar, absent with ecological explanation; question mark, answer uncertain. Published in June 1999 in Nature; Whiten et al "Cultures in Chimpanzees" [4].

Tool use, in particular, has been studied in chimpanzees.[57][58][59] The use of percussive tools, most commonly used to crack nuts, is a common example of tool use in chimpanzees and currently the only significant instance of behavioral differentiation between subspecies, as opposed to populations.[60][61] In foraging and hunting, chimpanzees often use probing sticks to collect insects or honey, though specific use varies by population.[62][63] In addition, chimpanzees have been known to fashion spears and lances, made of wood and sharpened with their teeth, to puncture prey (Fig. 5).[64]

Fig. 5: Field sample of lances fashioned by chimpanzees for hunting bushbabies in Senegal. Published in H. W. Greene's "Evolutionary Scenarios and Primate Natural History," 2017. Photo credits: J. Pruetz [5].

In hunting, chimpanzees and their demeanor can be more readily compared to members of the genus Homo than to other primates using similar methods, suggesting that genetics have played a role in tool use, despite common techniques among other primates.[65]


Contributions to Medicine and a Collective Understanding of Homo sapiens

Conclusion

Overall text length should be at least 1,000 words (before counting references), with at least 2 images. Include at least 5 references under Reference section.


References

  1. Bjork A, Liu W, Wertheim JO, Hahn BH, Worobey M. Evolutionary history of chimpanzees inferred from complete mitochondrial genomes. Mol Biol Evol. 2011;28(1):615–23.
  2. Raaum RL, Sterner KN, Noviello CM, Stewart CB, Disotell TR. Catarrhine primate divergence dates estimated from complete mitochondrial genomes: Concordance with fossil and nuclear DNA evidence. J Hum Evol. 2005;48(3):237–57.
  3. Stewart CB, Disotell TR. Primate evolution - In and out of Africa. Curr Biol. 1998;8(16):582–8.
  4. Raaum RL, Sterner KN, Noviello CM, Stewart CB, Disotell TR. Catarrhine primate divergence dates estimated from complete mitochondrial genomes: Concordance with fossil and nuclear DNA evidence. J Hum Evol. 2005;48(3):237–57.
  5. Bjork A, Liu W, Wertheim JO, Hahn BH, Worobey M. Evolutionary history of chimpanzees inferred from complete mitochondrial genomes. Mol Biol Evol. 2011;28(1):615–23.
  6. Raaum RL, Sterner KN, Noviello CM, Stewart CB, Disotell TR. Catarrhine primate divergence dates estimated from complete mitochondrial genomes: Concordance with fossil and nuclear DNA evidence. J Hum Evol. 2005;48(3):237–57.
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  10. Palaeontographica VA, Das P, Whiten a, Goodall J, Mcgrew WC, Nishida T, et al. Cultures in chimpanzees troglodytes ) have achieved long-term status across Africa , differ- lated 151 years of chimpanzee observation . This comprehensive analysis reveals patterns of variation that are far more extensive than have previously been docume. Nature. 1999;399(JUNE):15–8.
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Edited by [Author Name], student of Joan Slonczewski for BIOL 116 Information in Living Systems, 2020, Kenyon College.