Human beings have generated a system of cumulative cultural learning with great adaptive value. T... more Human beings have generated a system of cumulative cultural learning with great adaptive value. The evolution of this system required an increase in the capacity to innovate and to imitate in hominin lineage. However that development is costly and, moreover, imitation may restrain the adaptive advantage of a greater investment on innovation. We suggest that a possible way to overcome this problem in hominin evolution was parental teaching by evaluative feedback-i.e. assessor teaching. To explore this hypothesis we developed a mathematical model of cumulative cultural learning. We consider two cognitive levels, one Basic, with less ability to imitate and innovate, and the other Smart, with more ability of both. We study the transition from Basic to Smart in the absence or in presence of teaching. We also study the transition from no teaching to teaching at each cognitive level. We show that the transition to a Smart is easier in a teaching context than in one of only imitation. We also show that the transition to teaching is easier the greater the cognitive level.
Starting from a completely homozygous population of Drosophila melanogaster, two groups of 100 in... more Starting from a completely homozygous population of Drosophila melanogaster, two groups of 100 inbred lines each were established and maintained for 46 generations, by a single brother-sister mating and two double first cousin matings, respectively. Sternopleural bristle number, wing length and wing width were simultaneously scored in all lines every 4-5 generations. The means of four lines in each group departed significantly from the overall mean and, in each case, this was attributed to a single mutation of relatively large effect on at least one trait (0.3-1.4 environmental standard deviations in absolute value). Further analyses revealed widespread pleiotropy, similar gene action of a given mutation for all traits affected, and predominant additive action. No apparent association was found between the magnitudes of mutational effects on the traits and fitness. However, all recessive mutations were deleterious. The distribution of mutant effects was asymmetrical (positive for br...
The genetic architecture of complex human traits and diseases is affected by large number of poss... more The genetic architecture of complex human traits and diseases is affected by large number of possibly interacting genes, but detecting epistatic interactions can be challenging. In the last decade, several studies have alluded to problems that linkage disequilibrium can create when testing for epistatic interactions between DNA markers. However, these problems have not been formalized nor have their consequences been quantified in a precise manner. Here we use a conceptually simple three locus model involving a causal locus and two markers to show that imperfect LD can generate the illusion of epistasis, even when the underlying genetic architecture is purely additive. We describe necessary conditions for such “phantom epistasis” to emerge and quantify its relevance using simulations. Our empirical results demonstrate that phantom epistasis can be a very serious problem in GWAS studies (with rejection rates against the additive model greater than 0.28 for nominal p-values of 0.05, e...
A method for mapping complex trait genes using cDNA microarray and molecular marker data jointly ... more A method for mapping complex trait genes using cDNA microarray and molecular marker data jointly is presented and illustrated via simulation. We introduce a novel approach for simulating phenotypes and genotypes conditionally on real, publicly available, microarray data. The model assumes an underlying continuous latent variable (liability) related to some measured cDNA expression levels. Partial least-squares logistic regression is used to estimate the liability under several scenarios where the level of gene interaction, the gene effect, and the number of cDNA levels affecting liability are varied. The results suggest that: (1) the usefulness of microarray data for gene mapping increases when both the number of cDNA levels in the underlying liability and the QTL effect decrease and when genes are coexpressed; (2) the correlation between estimated and true liability is large, at least under our simulation settings; (3) it is unlikely that cDNA clones identified as significant with ...
Abstract Text: In this study, genomic estimates of inbreeding, coancestry and effective populatio... more Abstract Text: In this study, genomic estimates of inbreeding, coancestry and effective population size in the Spanish Holstein population were obtained. Genomic estimates of inbreeding included those obtained on a marker-by-marker basis and those based on runs of homozygosity. Genomic estimates were compared with those obtained from genealogical information. The results indicate that the regression coefficient of genomic inbreeding on genealogical inbreeding was higher than the regression coefficient of genealogical inbreeding on genomic inbreeding. Similar results were also observed for coancestry. Additionally, inbreeding estimates based on runs of homozygosity tend to reflect identity by descent status better than estimates obtained on a marker-by-marker basis. Estimates of effective population size obtained from genomic and genealogical information were consistent and ranged from about 66 to 79. These values highlight the need of controlling the rate of coancestry and inbreedin...
Las tradiciones que configuran el cuerpo central de teoría en las ciencias sociales comparten la ... more Las tradiciones que configuran el cuerpo central de teoría en las ciencias sociales comparten la convicción de que las culturas constituyen sistemas que pueden ser interpretados sin tener en cuenta las características psicobiológicas de la naturaleza humana. Frente a esto, desde hace unos años, distintas aproximaciones naturalistas, como la psicología evolucionista y la teoría de la herencia dual, han logrado construir modelos bastante sólidos en el análisis de la cultura. Aquí se revisan brevemente los elementos básicos de esos modelos y, en la parte final del artículo, se presenta una propuesta alternativa basada en lo que denominamos el aprendizaje social asesor.
Proceedings of the National Academy of Sciences, 2004
Cultural transmission in our species works most of the time as a cumulative inheritance system al... more Cultural transmission in our species works most of the time as a cumulative inheritance system allowing members of a group to incorporate behavioral features not only with a positive biological value but sometimes also with a neutral, or even negative, biological value. Most of models of dual inheritance theory and gene-culture coevolution suggest that an increase, either qualitative or quantitative, in the efficiency of imitation is the key factor to explain the transformation of primate social learning in a cumulative cultural system of inheritance as it happens during hominization. We contend that more efficient imitation is necessary but not enough for this transformation to occur and that the key factor enabling such a transformation is that some hominids developed the capacity to approve or disapprove their offspring's learned behavior. This capacity to approve or disapprove offspring's behavior makes learning both less costly and more accurate, and it transformed the ...
The genetic variability for RAPDs band pattern was studied in a set of 157 mutation accumulation ... more The genetic variability for RAPDs band pattern was studied in a set of 157 mutation accumulation (MA) lines of Drosophila melanogaster. These MA lines were derived from the same isogenic base population and subsequently maintained by full-sib mating during 132 generations. The ancestral pattern of the original isogenic base can be unambiguously established as the consensus pattern of the MA lines and, because these lines are expected to be homozygous, dominance for band pattern is not a concern. Only repeatable changes in band pattern were considered. The number of ancestral bands detected implies that ninenucleotide targets are enough for repeatable PCR amplification. Compared with the ancestral pattern, one MA line lost one band and two MA lines gained a new one. These results can be accounted for by the insertion of transposable elements occurring at a rate 0.07 , i , 0.21 per whole haploid genome and generation. This range is typical for Drosophila and consistent with the previously observed mobility for the roo family, supporting the generality of previous estimates of spontaneous mutation rates for morphological and fitness traits based on these MA lines. The sequence of one of the new bands suggests that the Idefix family is also active in the lines.
In Tribolium castaneum (CS) and T. confusum (CF), intra-and interspeci®c rates of homosexual moun... more In Tribolium castaneum (CS) and T. confusum (CF), intra-and interspeci®c rates of homosexual mounting have been measured. The intraspeci®c results are compatible with the hypothesis of both species being sexually indiscriminate. However, the CF intraspeci®c rates were very high (35%±53% of mountings were homosexual), suggesting a lower sexual attractiveness, or a stronger rejection to being mounted, of CF females relative to conspeci®c males. CS males discriminate between species but, in interspeci®c contacts, preferentially mounted CF males rather than CF females. CF males do not discriminate between species, but the loss of sexual attractiveness of CF females, or their rejection to being mounted, may act as a precopulatory isolation mechanism.
Humans have developed the capacity to approve or disapprove of the behavior of their children and... more Humans have developed the capacity to approve or disapprove of the behavior of their children and of unrelated individuals. The ability to approve or disapprove transformed social learning into a system of cumulative cultural inheritance, because it increased the reliability of cultural transmission. Moreover, people can transmit their behavioral experiences (regarding what can and cannot be done) to their offspring, thereby avoiding the costs of a laborious, and sometimes dangerous, evaluation of different cultural alternatives. Our thesis is that, during ontogeny, the evaluative communication (approval/disapproval) between parents and offspring is substituted by other evaluative communications among peers, like individuals of the same generation. Each person belongs to a reference social group with individuals that interact more intensively. Humans have developed psychological mechanisms that enable cultural transmission by being receptive to parental advice as well as their reference social group. The selective pressure that promoted these new evaluative interactions arose to facilitate the establishment of efficient cooperative relationships. In short, the social control of behavior is essential to understand human cultural transmission.
This paper presents the hypothesis that linguistic capacity evolved through the action of natural... more This paper presents the hypothesis that linguistic capacity evolved through the action of natural selection as an instrument which increased the efficiency of the cultural transmission system of early hominids. We suggest that during the early stages of hominization, hominid social learning, based on indirect social learning mechanisms and true imitation, came to constitute cumulative cultural transmission based on true imitation and the approval or disapproval of the learned behaviour of offspring. A key factor for this transformation was the development of a conceptual capacity for categorizing learned behaviour in value terms-positive or negative, good or bad. We believe that some hominids developed this capacity for categorizing behaviour, and such an ability allowed them to approve or disapprove of their offsprings' learned behaviour. With such an ability, hominids were favoured, as they could transmit to their offspring all their behavioural experience about what can and cannot be done. This capacity triggered a cultural transmission system similar to the human one, though pre-linguistic. We suggest that the adaptive advantage provided by this new system of social learning generated a selection pressure in favour of the development of a linguistic capacity allowing children to better understand the new kind of evaluative information received from parents.
The rate of homosexual copulation has been defined as the ratio between the number of homosexual ... more The rate of homosexual copulation has been defined as the ratio between the number of homosexual mountings and the total number of mountings (homo and heterosexual) performed by a Tribolium castaneum male during a period of 30 min. In a laboratory population, the average rate when a number of males (m) and females (k x m) are tested together has been estimated in each of the six situations defined by m = 2 and 10 and k = 0.5, 1, and 2, k being the sex ratio among scored individuals. Good agreement was found between the observed rates of homosexual copulation and those expected assuming random contacts between pairs of individuals totally indiscriminate with respect to sex. The genetic properties of the trait have been investigated by means of a diallel analysis of six highly inbred lines derived from the same population and their F1 crosses. Significant general and specific combining ability effects were detected. When noninbred females were used for testing, the rate of homosexual copulation is expected to be higher for inbred than for noninbred males. This prediction, implying the existence of inbreeding depression for the trait, also was confirmed by the data.
INTRODUCTION The concept of coancestry (or kinship) between two individuals plays a central role ... more INTRODUCTION The concept of coancestry (or kinship) between two individuals plays a central role in animal breeding in order to estimate genetic parameters and to carry out genetic evaluations (Falconer and Mackay, 1996) and in the field of conservation, to decide which animals will contribute gametes to the next generation and how the matings will be organised (Caballero and Toro, 2000). As a consequence of the great interest produced by the development of molecular markers several estimators have been developed to measure pairwise coancestry using the molecular information. Most of them are described in Lynch and Ritland (1999) and Toro et al. (2002) and their performance compared by computer simulation. In the last work several estimators were calculated for 62 individuals genotyped for 49 microsatellite loci and their values compared with the genealogical coancestry calculated from the complete pedigree. Here we analyse with more detail some of them and the implications of their...
Human beings have generated a system of cumulative cultural learning with great adaptive value. T... more Human beings have generated a system of cumulative cultural learning with great adaptive value. The evolution of this system required an increase in the capacity to innovate and to imitate in hominin lineage. However that development is costly and, moreover, imitation may restrain the adaptive advantage of a greater investment on innovation. We suggest that a possible way to overcome this problem in hominin evolution was parental teaching by evaluative feedback-i.e. assessor teaching. To explore this hypothesis we developed a mathematical model of cumulative cultural learning. We consider two cognitive levels, one Basic, with less ability to imitate and innovate, and the other Smart, with more ability of both. We study the transition from Basic to Smart in the absence or in presence of teaching. We also study the transition from no teaching to teaching at each cognitive level. We show that the transition to a Smart is easier in a teaching context than in one of only imitation. We also show that the transition to teaching is easier the greater the cognitive level.
Starting from a completely homozygous population of Drosophila melanogaster, two groups of 100 in... more Starting from a completely homozygous population of Drosophila melanogaster, two groups of 100 inbred lines each were established and maintained for 46 generations, by a single brother-sister mating and two double first cousin matings, respectively. Sternopleural bristle number, wing length and wing width were simultaneously scored in all lines every 4-5 generations. The means of four lines in each group departed significantly from the overall mean and, in each case, this was attributed to a single mutation of relatively large effect on at least one trait (0.3-1.4 environmental standard deviations in absolute value). Further analyses revealed widespread pleiotropy, similar gene action of a given mutation for all traits affected, and predominant additive action. No apparent association was found between the magnitudes of mutational effects on the traits and fitness. However, all recessive mutations were deleterious. The distribution of mutant effects was asymmetrical (positive for br...
The genetic architecture of complex human traits and diseases is affected by large number of poss... more The genetic architecture of complex human traits and diseases is affected by large number of possibly interacting genes, but detecting epistatic interactions can be challenging. In the last decade, several studies have alluded to problems that linkage disequilibrium can create when testing for epistatic interactions between DNA markers. However, these problems have not been formalized nor have their consequences been quantified in a precise manner. Here we use a conceptually simple three locus model involving a causal locus and two markers to show that imperfect LD can generate the illusion of epistasis, even when the underlying genetic architecture is purely additive. We describe necessary conditions for such “phantom epistasis” to emerge and quantify its relevance using simulations. Our empirical results demonstrate that phantom epistasis can be a very serious problem in GWAS studies (with rejection rates against the additive model greater than 0.28 for nominal p-values of 0.05, e...
A method for mapping complex trait genes using cDNA microarray and molecular marker data jointly ... more A method for mapping complex trait genes using cDNA microarray and molecular marker data jointly is presented and illustrated via simulation. We introduce a novel approach for simulating phenotypes and genotypes conditionally on real, publicly available, microarray data. The model assumes an underlying continuous latent variable (liability) related to some measured cDNA expression levels. Partial least-squares logistic regression is used to estimate the liability under several scenarios where the level of gene interaction, the gene effect, and the number of cDNA levels affecting liability are varied. The results suggest that: (1) the usefulness of microarray data for gene mapping increases when both the number of cDNA levels in the underlying liability and the QTL effect decrease and when genes are coexpressed; (2) the correlation between estimated and true liability is large, at least under our simulation settings; (3) it is unlikely that cDNA clones identified as significant with ...
Abstract Text: In this study, genomic estimates of inbreeding, coancestry and effective populatio... more Abstract Text: In this study, genomic estimates of inbreeding, coancestry and effective population size in the Spanish Holstein population were obtained. Genomic estimates of inbreeding included those obtained on a marker-by-marker basis and those based on runs of homozygosity. Genomic estimates were compared with those obtained from genealogical information. The results indicate that the regression coefficient of genomic inbreeding on genealogical inbreeding was higher than the regression coefficient of genealogical inbreeding on genomic inbreeding. Similar results were also observed for coancestry. Additionally, inbreeding estimates based on runs of homozygosity tend to reflect identity by descent status better than estimates obtained on a marker-by-marker basis. Estimates of effective population size obtained from genomic and genealogical information were consistent and ranged from about 66 to 79. These values highlight the need of controlling the rate of coancestry and inbreedin...
Las tradiciones que configuran el cuerpo central de teoría en las ciencias sociales comparten la ... more Las tradiciones que configuran el cuerpo central de teoría en las ciencias sociales comparten la convicción de que las culturas constituyen sistemas que pueden ser interpretados sin tener en cuenta las características psicobiológicas de la naturaleza humana. Frente a esto, desde hace unos años, distintas aproximaciones naturalistas, como la psicología evolucionista y la teoría de la herencia dual, han logrado construir modelos bastante sólidos en el análisis de la cultura. Aquí se revisan brevemente los elementos básicos de esos modelos y, en la parte final del artículo, se presenta una propuesta alternativa basada en lo que denominamos el aprendizaje social asesor.
Proceedings of the National Academy of Sciences, 2004
Cultural transmission in our species works most of the time as a cumulative inheritance system al... more Cultural transmission in our species works most of the time as a cumulative inheritance system allowing members of a group to incorporate behavioral features not only with a positive biological value but sometimes also with a neutral, or even negative, biological value. Most of models of dual inheritance theory and gene-culture coevolution suggest that an increase, either qualitative or quantitative, in the efficiency of imitation is the key factor to explain the transformation of primate social learning in a cumulative cultural system of inheritance as it happens during hominization. We contend that more efficient imitation is necessary but not enough for this transformation to occur and that the key factor enabling such a transformation is that some hominids developed the capacity to approve or disapprove their offspring's learned behavior. This capacity to approve or disapprove offspring's behavior makes learning both less costly and more accurate, and it transformed the ...
The genetic variability for RAPDs band pattern was studied in a set of 157 mutation accumulation ... more The genetic variability for RAPDs band pattern was studied in a set of 157 mutation accumulation (MA) lines of Drosophila melanogaster. These MA lines were derived from the same isogenic base population and subsequently maintained by full-sib mating during 132 generations. The ancestral pattern of the original isogenic base can be unambiguously established as the consensus pattern of the MA lines and, because these lines are expected to be homozygous, dominance for band pattern is not a concern. Only repeatable changes in band pattern were considered. The number of ancestral bands detected implies that ninenucleotide targets are enough for repeatable PCR amplification. Compared with the ancestral pattern, one MA line lost one band and two MA lines gained a new one. These results can be accounted for by the insertion of transposable elements occurring at a rate 0.07 , i , 0.21 per whole haploid genome and generation. This range is typical for Drosophila and consistent with the previously observed mobility for the roo family, supporting the generality of previous estimates of spontaneous mutation rates for morphological and fitness traits based on these MA lines. The sequence of one of the new bands suggests that the Idefix family is also active in the lines.
In Tribolium castaneum (CS) and T. confusum (CF), intra-and interspeci®c rates of homosexual moun... more In Tribolium castaneum (CS) and T. confusum (CF), intra-and interspeci®c rates of homosexual mounting have been measured. The intraspeci®c results are compatible with the hypothesis of both species being sexually indiscriminate. However, the CF intraspeci®c rates were very high (35%±53% of mountings were homosexual), suggesting a lower sexual attractiveness, or a stronger rejection to being mounted, of CF females relative to conspeci®c males. CS males discriminate between species but, in interspeci®c contacts, preferentially mounted CF males rather than CF females. CF males do not discriminate between species, but the loss of sexual attractiveness of CF females, or their rejection to being mounted, may act as a precopulatory isolation mechanism.
Humans have developed the capacity to approve or disapprove of the behavior of their children and... more Humans have developed the capacity to approve or disapprove of the behavior of their children and of unrelated individuals. The ability to approve or disapprove transformed social learning into a system of cumulative cultural inheritance, because it increased the reliability of cultural transmission. Moreover, people can transmit their behavioral experiences (regarding what can and cannot be done) to their offspring, thereby avoiding the costs of a laborious, and sometimes dangerous, evaluation of different cultural alternatives. Our thesis is that, during ontogeny, the evaluative communication (approval/disapproval) between parents and offspring is substituted by other evaluative communications among peers, like individuals of the same generation. Each person belongs to a reference social group with individuals that interact more intensively. Humans have developed psychological mechanisms that enable cultural transmission by being receptive to parental advice as well as their reference social group. The selective pressure that promoted these new evaluative interactions arose to facilitate the establishment of efficient cooperative relationships. In short, the social control of behavior is essential to understand human cultural transmission.
This paper presents the hypothesis that linguistic capacity evolved through the action of natural... more This paper presents the hypothesis that linguistic capacity evolved through the action of natural selection as an instrument which increased the efficiency of the cultural transmission system of early hominids. We suggest that during the early stages of hominization, hominid social learning, based on indirect social learning mechanisms and true imitation, came to constitute cumulative cultural transmission based on true imitation and the approval or disapproval of the learned behaviour of offspring. A key factor for this transformation was the development of a conceptual capacity for categorizing learned behaviour in value terms-positive or negative, good or bad. We believe that some hominids developed this capacity for categorizing behaviour, and such an ability allowed them to approve or disapprove of their offsprings' learned behaviour. With such an ability, hominids were favoured, as they could transmit to their offspring all their behavioural experience about what can and cannot be done. This capacity triggered a cultural transmission system similar to the human one, though pre-linguistic. We suggest that the adaptive advantage provided by this new system of social learning generated a selection pressure in favour of the development of a linguistic capacity allowing children to better understand the new kind of evaluative information received from parents.
The rate of homosexual copulation has been defined as the ratio between the number of homosexual ... more The rate of homosexual copulation has been defined as the ratio between the number of homosexual mountings and the total number of mountings (homo and heterosexual) performed by a Tribolium castaneum male during a period of 30 min. In a laboratory population, the average rate when a number of males (m) and females (k x m) are tested together has been estimated in each of the six situations defined by m = 2 and 10 and k = 0.5, 1, and 2, k being the sex ratio among scored individuals. Good agreement was found between the observed rates of homosexual copulation and those expected assuming random contacts between pairs of individuals totally indiscriminate with respect to sex. The genetic properties of the trait have been investigated by means of a diallel analysis of six highly inbred lines derived from the same population and their F1 crosses. Significant general and specific combining ability effects were detected. When noninbred females were used for testing, the rate of homosexual copulation is expected to be higher for inbred than for noninbred males. This prediction, implying the existence of inbreeding depression for the trait, also was confirmed by the data.
INTRODUCTION The concept of coancestry (or kinship) between two individuals plays a central role ... more INTRODUCTION The concept of coancestry (or kinship) between two individuals plays a central role in animal breeding in order to estimate genetic parameters and to carry out genetic evaluations (Falconer and Mackay, 1996) and in the field of conservation, to decide which animals will contribute gametes to the next generation and how the matings will be organised (Caballero and Toro, 2000). As a consequence of the great interest produced by the development of molecular markers several estimators have been developed to measure pairwise coancestry using the molecular information. Most of them are described in Lynch and Ritland (1999) and Toro et al. (2002) and their performance compared by computer simulation. In the last work several estimators were calculated for 62 individuals genotyped for 49 microsatellite loci and their values compared with the genealogical coancestry calculated from the complete pedigree. Here we analyse with more detail some of them and the implications of their...
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Papers by Miguel Toro