Long Interspersed Element 1 (L1) is a retrotransposon that comprises ;17% of the human genome. Despite its abundance in mammalian genomes, relatively little is understood about L1 retrotransposition in vivo. To study the timing and tissue specificity of retrotransposition, we created transgenic mouse and rat models containing human or mouse L1 elements controlled by their endogenous promoters. Here, we demonstrate abundant L1 RNA in both germ cells and embryos. However, the integration events usually occur in embryogenesis rather than in germ cells and are not heritable. We further demonstrate L1 RNA in preimplantation embryos lacking the L1 transgene and L1 somatic retrotransposition events in blastocysts and adults lacking the transgene. Together, these data indicate that L1 RNA transcribed in male or female germ cells can be carried over through fertilization and integrate during embryogenesis, an interesting example of heritability of RNA independent of its encoding DNA. Thus, L1 creates somatic mosaicism during mammalian development, suggesting a role for L1 in carcinogenesis and other disease.[Keywords: Retrotransposon; Line-1; somatic mosaicism; RNA carryover] Supplemental material is available at http://www.genesdev.org.

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An important extension to our understanding of evolutionary processes has been the discovery of the roles that individual and social learning play in creating recurring phenotypes on which selection can act. Cultural change occurs chiefly through invention of new behavioral variants combined with social transmission of the novel behaviors to new practitioners. Therefore, understanding what makes some individuals more likely to innovate and/or transmit new behaviors is critical for creating realistic models of culture change. The difficulty in identifying what behaviors qualify as new in wild animal populations has inhibited researchers from understanding the characteristics of behavioral innovations and innovators. Here, we present the findings of a long-term, systematic study of innovation (10 y, 10 groups, and 234 individuals) in wild capuchin monkeys (Cebus capucinus) in Lomas Barbudal, Costa Rica. Our methodology explicitly seeks novel behaviors, requiring their absence during the first 5 y of the study to qualify as novel in the second 5 y of the study. Only about 20% of 187 innovations identified were retained in innovators' individual behavioral repertoires, and 22% were subsequently seen in other group members. Older, more social monkeys were more likely to invent new forms of social interaction, whereas younger monkeys were more likely to innovate in other behavioral domains (foraging, investigative, and self-directed behaviors). Sex and rank had little effect on innovative tendencies. Relative to apes, capuchins devote more of their innovations repertoire to investigative behaviors and social bonding behaviors and less to foraging and comfort behaviors.innovation | Cebus capucinus | cultural evolution | phenotypic plasticity | learning B ehavioral innovation has long been a topic of interest for researchers dedicated to studying the evolution of culture, because it is a driver of cultural change (1, 2). The types of behavioral traditions that are of greatest interest to evolutionary modelers are those starting with an innovation that then spreads via social learning. Understanding the characteristics of (i) behavioral innovations (which are roughly analogous to genetic mutations) and (ii) the individuals who invent these behaviors is critical to understanding cultural evolution and its relationship to genetic evolution. Innovation is also of interest to evolutionary biologists who study the role that learning plays in macroevolution, because it is a type of phenotypic plasticity that can affect the direction of natural selection (3). Ability to innovate can enhance reproductive success (for example, by enabling individuals to exploit new resources) (4-6). Innovation can generate the Baldwin effect, in which learned traits create recurring phenotypes that select for morphological adaptations, eventually leading to speciation (3, 7). Innovation is also of interest as a correlate of intelligence more generally, and the ability to solve novel cognitive problems presented by experimenters can be positively ...

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Documenting inbreeding and its potential costs in wild populations is a complicated matter. Early infant death before genetic samples can be collected limits the ability of researchers to measure fitness costs, and pedigree information is necessary to accurately estimate relatedness between breeding individuals. Using data from 25 years of research from the Lomas Barbudal Capuchin Monkey Project, and a sample of 109 females that have given birth, we find that despite frequent co-residency of adult opposite-sexed individuals, capuchins produce offspring with close kin (i.e. related at the half sibling level or higher) less often than would be expected in the absence of inbreeding avoidance. We do not find support for alternative, non-behavioral explanations for this pattern and thus argue for mate choice. Furthermore, we find evidence for fitness costs among inbred animals in the form of delayed female age at first birth, but not significantly higher juvenile mortality. Further research is necessary in order to determine the mechanisms by which individuals develop sexual aversion to close kin. Significance Statement: Through a combination of demographic records, maternal pedigrees, and genetically determined paternity, this study provides a detailed study of inbreeding and inbreeding avoidance in a well-studied mammal population. This study provides (1) evidence that capuchin monkeys avoid mating with close kin at both the level of daughter-father and half sibling, and (2) evidence of fitness costs to inbreeding in the form of delayed first age at reproduction.

The ability to recognize kin has important impacts on fitness because it can allow for kinbiased affiliative behaviors and for avoidance of mating with close kin. While the presence and effects of kin biases have been widely studied, less is known about the process by which animals recognize close kin. Here we investigate potential cues that white-faced capuchin monkeys (Cebus capucinus) may use to detect half-siblings and closer kin. We focus on the first year of life in a sample of 130 infant (n=65 infant females) wild capuchins from the Lomas Barbudal population in Costa Rica. We show that (1) infant relatedness to juvenile and adult males at the level of half-sibling and higher can be predicted by male alpha status, spatial proximity, and age proximity, and that (2) infant relatedness to juvenile and adult females at the level of half-sibling or higher can be predicted by spatial proximity (but not age proximity). Furthermore, (1) the identities of infants' fathers can also be predicted by male alpha status and the spatial proximity between infants and adult males, and (2) age proximity (but not spatial proximity) is predictive of paternal sibship. These results suggest that infant capuchins have access to multiple cues to close relatedness and paternal kinship, though whether infants use these cues later in life remains to be explored in future research.Keywords: kin recognition, age proximity, early social familiarity, male dominance, The ability to recognize kin has many adaptive benefits. It can help organisms increase their inclusive fitness by allowing them to allot a disproportionate amount of affiliative behaviors and coalitionary support toward individuals with which they share a larger proportion of their genes (Hamilton, 1964). Furthermore, by allowing individuals to recognize kin and discriminate against them in a mating context, kin recognition mechanisms can facilitate avoidance of the deleterious effects of close inbreeding (Charlesworth & Charlesworth, 1987).We define kin recognition as the ability to identify and distinguish kin from non-kin, or more closely related kin from more distant kin, regardless of the mechanism or mechanisms through which it is accomplished, and regardless of whether it actually leads to differential treatment of individuals (i.e. kin discrimination). In this sense, we take on a broad as opposed to narrow definition of kin recognition (see Penn & Frommen, 2010). We consider the related term kin bias to be the differential treatment of kin versus non-kin (or close kin from distant kin), though not exclusively as the result of kin recognition.Kin recognition has been documented in a wide array of animal taxa, including, to name only a few: Artic charr (Salvelinus alpinus) (Winberg & Olsén, 1992;Olsén & Winberg, 1996), spadefoot toads (Scaphiopus bombifrons) (Pfennig et al., 1993), Golden hamsters (Mesocricetus auratus) (Mateo & Johnston, 2000), and Belding's ground squirrels (Spermophilus beldingi) and Arctic ground squirrels (Spermophilus parryii) (Holmes & S...

It is rare in studies of long-lived animals to know enough about the personalities and early experiences of individuals to use this information to predict their behavior during major life transitions in adolescence and adulthood. Here, we examine how personality traits and early experiences predict age of natal emigration and timing of first ascent to alpha status in 169 wild male white-faced capuchins studied at Lomas Barbudal, Costa Rica, 75 of whom emigrated and 23 of whom acquired alpha status.Males were more likely to delay natal emigration if they were more extraverted, more neurotic, if their fathers co-resided longer with them, and if there were fewer alpha male turnovers. More extraverted males attained alpha status sooner.

To address claims of human exceptionalism, we determine where humans fit within the greater mammalian distribution of reproductive inequality. We show that humans exhibit lower reproductive skew (i.e., inequality in the number of surviving offspring) among males and smaller sex differences in reproductive skew than most other mammals, while nevertheless falling within the mammalian range. Additionally, female reproductive skew is higher in polygynous human populations than in polygynous nonhumans mammals on average. This patterning of skew can be attributed in part to the prevalence of monogamy in humans compared to the predominance of polygyny in nonhuman mammals, to the limited degree of polygyny in the human societies that practice it, and to the importance of unequally held rival resources to women’s fitness. The muted reproductive inequality observed in humans appears to be linked to several unusual characteristics of our species—including high levels of cooperation among males, high dependence on unequally held rival resources, complementarities between maternal and paternal investment, as well as social and legal institutions that enforce monogamous norms.