Piecing together the problems in diagnosing low-level chromosomal mosaicism

Low-level somatic chromosomal mosaicism, which usually arises from post-zygotic errors, is a known cause of several well defined genetic syndromes and has been implicated in various multifactorial diseases. It is, however, not easy to diagnose, as various physical and technical factors complicate its identification

A case of intercommunity lethal aggression by chimpanzees in an open and dry landscape, Issa Valley, western Tanzania

Intercommunity (lethal) aggression is a familiar component of the behavioural repertoire of many forest-dwelling chimpanzee (Pan troglodytes) communities. However, until now, the absence of intercommunity attacks - including killings - in communities that live in open, mosaic environments has supported hypotheses of reduced resource competition in drier habitats, and informed referential models of early hominin social dynamics in a similar habitat. In June 2020, we observed the first instance of intercommunity lethal aggression, a male-committed infanticide, by the Issa chimpanzee community, which live in a savannah-mosaic habitat in the Issa Valley, western Tanzania. The carcass was recovered by researchers after it was abandoned by the attackers. Here, we give a detailed account of the events leading up to and including the infanticide, and contextualise our observations with what has been described for other chimpanzee communities. Notably, in contrast to the majority of reported intercommunity infanticides, the infant male victim was castrated (and not cannibalised), making this the youngest reported castration. This observation of intercommunity aggression disproves its hypothesised absence in savannah-dwelling chimpanzees, which by extension, has implications for early hominin evolution. We suggest that the near absence of observations of intercommunity aggression in savannah chimpanzee communities is most likely due to the lack of long-term study communities, and in some cases geographic isolation. We hypothesise that food-rich areas within a habitat with otherwise widely distributed food sources may select for intense intercommunity aggression despite the low population density characteristic of savannah communities. Anecdotes such as this add to the comparative database available on intercommunity killings in chimpanzee society, improving our ability to draw inferences about their evolutionary significance

Meiotic errors followed by two parallel postzygotic trisomy rescue events are a frequent cause of constitutional segmental mosaicism

Structural copy number variation (CNV) is a frequent cause of human variation and disease. Evidence is mounting that somatic acquired CNVs are prevalent, with mosaicisms of large segmental CNVs in blood found in up to one percent of both the healthy and patient populations. It is generally accepted that such constitutional mosaicisms are derived from postzygotic somatic mutations. However, few studies have tested this assumption. Here we determined the origin of CNVs which coexist with a normal cell line in nine individuals. We show that in 2/9 the CNV originated during meiosis. The existence of two cell lines with 46 chromosomes thus resulted from two parallel trisomy rescue events during postzygotic mitoses

Orangutans have larger gestural repertoires in captivity than in the wild—A case of weak innovation?

Whether nonhuman species can change their communicative repertoire in response to socio-ecological environments has critical implications for communicative innovativeness prior to the emergence of human language, with its unparalleled productivity. Here, we use a comparative sample of wild and zoo-housed orangutans of two species (Pongo abelii, Pongo pygmaeus) to assess the effect of the wild-captive contrast on repertoires of gestures and facial expressions. We find that repertoires on both the individual and population levels are larger in captive than in wild settings, regardless of species, age class, or sampling effort. In the more sociable Sumatran species, dominant use of signals toward single outcomes was also higher in captive settings. We thus conclude that orangutans exposed to more sociable and terrestrial conditions evince behavioral plasticity, in that they produce additional innate or innovated signals that are highly functionally specific. These findings suggest a latent capacity for innovativeness in these apes' communicative repertoires

The function and evolution of child-directed communication

Funding: Writing this article was supported by the National Centre of Competence in Research (NCCR) Evolving Language, Swiss National Science Foundation Agreement 51NF40 180888 for JS, CF, FW, KZ, CPvS, SWT and SS. SWT was additionally funded by Swiss National Science Foundation grant PP00P3_198912.Humans communicate with small children in unusual and highly conspicuous ways (child- directed communication (CDC)), which enhance social bonding and facilitate language acquisition. CDC-like inputs are also reported for some vocally learning animals, suggesting similar functions in facilitating communicative competence. However, adult great apes, our closest living relatives, rarely signal to their infants, implicating communication surrounding the infant as the main input for infant great apes and early humans. Given cross-cultural variation in the amount and structure of CDC, we suggest that child-surrounding communication (CSC) provides essential compensatory input when CDC is less prevalent—a paramount topic for future studies.Publisher PDFNon peer reviewe

Interactions Between Chimpanzees (Pan troglodytes schweinfurthii) and Cattle (Bos taurus) in the Issa Valley, Western Tanzania

Wildlife habitats are being degraded globally due to human activities. Pastoralism in Africa has been described as a major threat to habitats and a source of wildlife-livestock interactions and conflict. Chimpanzees in particular are affected by the use of land for livestock, most notably where cattle trample terrestrial food sources and may act as potential reservoirs of disease. Yet, despite extensive study of wild chimpanzees across their distribution, no detailed behavioural observations of chimpanzee-cattle interactions have been described. We report ten direct chimpanzee-cattle encounters that occurred from 2019-2021 in the Issa valley, Tanzania. We observed more interactions in the dry season, and these prompted more vigilance by chimpanzees than wet season interactions. The distance between chimpanzees and cattle may also affect chimpanzee behavioural responses. Our observations suggest that (1) chimpanzees remain vigilant but otherwise only minimally change their behavioural reactions towards cattle in ways that depend, at least in part, on chimpanzee party composition, with males reacting more overtly than females and (2) chimpanzees exhibit more aversive behaviour when cattle are accompanied by herders and dogs

The function and evolution of child-directed communication

Humans communicate with small children in unusual and highly conspicuous ways (child-directed communication (CDC)), which enhance social bonding and facilitate language acquisition. CDC-like inputs are also reported for some vocally learning animals, suggesting similar functions in facilitating communicative competence. However, adult great apes, our closest living relatives, rarely signal to their infants, implicating communication surrounding the infant as the main input for infant great apes and early humans. Given cross-cultural variation in the amount and structure of CDC, we suggest that child-surrounding communication (CSC) provides essential compensatory input when CDC is less prevalent—a paramount topic for future studies

Isolation rearing does not constrain social plasticity in a family-living lizard

Financial support for this research was provided by the Australian Research Council (ARC DP130102998, grant to MJW and RWB), Natural Sciences and Engineering Research Council of Canada (scholarship to JLR), the Australasian Society for the Study of Animal Behavior, the Australian Museum, and Macquarie University (scholarship to JLR). DWAN was supported by an ARC Discovery Early Career Research Award (DE150101774) and University of New South Wales Vice Chancellors Fellowship.An animal’s social environment can be both dynamic and complex. Thus, social species often garner fitness benefits through being plastic in their social behavior. Yet, social plasticity can be constrained by an individual’s experience. We examined the influence of early social environment on social behavior in the tree skink (Egernia striolata), a family-living lizard. In the first phase of this study, we reared juveniles in 2 different social environments for 1.5 years: either in isolation or in unrelated pairs. We quantified each lizard’s sociability at 4-month intervals using a standardized laboratory assay and found that isolated lizards were more sociable, spending the assay closer to an adult female, than socially-reared lizards. In the second phase of this study (at the end of 1.5 years), we released all lizards into a semi-natural environment, observed their associations, and used social network analysis to quantify social behavior. During the initial 6 weeks post-release, we detected no differences in social behavior between rearing treatments. However, during the following 6 months differences emerged. Isolated lizards were more homogeneous in the strength of their associations than socially-reared lizards. Also, at first, isolated lizards associated more strongly than socially-reared lizards. Over time, isolated lizard associations became weaker and involved fewer lizards. In contrast, the level and number of associations of socially-reared lizards were stable over time. Our findings suggest that early experience influences tree skink social behavior but does not constrain social plasticity: isolation rearing did not limit their ability to respond to a novel social environment.PostprintPeer reviewe