http://www.sciencedaily.com/releases/2009/06/090618180334.htm
ScienceDaily (July 8, 2009) — Darwin's theory of evolution predicts that men will take more care of children that look like them. A team at the Institut des sciences de l'évolution (CNRS / Université de Montpellier 2) verified this prediction in a study published online in the pre-print issue of the journal Animal Behaviour.
The investment of a father in the care and education of a child is a decisive factor for the child's development, growth and even survival, particularly in countries with high infant mortality. As this behavior is transmitted from generation to generation, it can evolve by natural selection. Evolutionary theory predicts that men should have developed the capacity to recognise their biological children. This recognition of paternity can be made on the basis of physical resemblance.
The study by the ISEM(1) team has shown for the first time that paternal investment is partly influenced by genetically based similarities.
The study was conducted in several villages in Senegal, where the researchers used a method that simultaneously quantified investment made by fathers and their resemblance to their children. A total of thirty families, each with two children, took part in the study. To quantify paternal investment, mothers answered a questionnaire in which they had to estimate the time that the father spent looking after the child, his attention, affection and even the money he provided.
According to their answers, each father was assigned an investment index. A separate group of people, who did not know these families, were chosen as relatedness 'raters' to evaluate facial and olfactory resemblance between children and fathers. For the faces, a photograph of each child was shown to the raters, together with those of three men including the father. For odor, the evaluator had to compare the odors of a tee-shirt worn by the child with those of two men. Each time that the father was recognized, a point was attributed and these results were collated to build a resemblance index.
A correlation was found between these resemblance indices and the paternal investment as calculated from the questionnaire results. The study also clearly confirmed the positive impact of a father's presence on the nutrition and growth of the child. In this region, children who benefit from the presence of their father clearly have better living conditions.
From the point of view of Darwinian theory, very few studies have been made on the link between paternal investment and genetically based resemblance, and none have been done with real families. Today, these results represent an important step in the study of the evolution of paternal investment. The ISEM team has also conducted a study on paternal investment in France from which results will be published in the coming months.
1) Institut des sciences de l'évolution de Montpellier (CNRS / Université de Montpellier)
Journal reference:
Alvergne et al. Father-offspring resemblance predicts paternal investment in humans. Animal Behaviour, May 28, 2009; DOI: 10.1016/j.anbehav.2009.03.019
Showing posts with label body structure. Show all posts
Showing posts with label body structure. Show all posts
Wednesday, July 8, 2009
Wednesday, June 3, 2009
New Hominid 12 Million Years Old Found In Spain, With 'Modern' Facial Features
http://www.sciencedaily.com/releases/2009/06/090602083729.htm
ScienceDaily (June 2, 2009) — Researchers have discovered a fossilized face and jaw from a previously unknown hominoid primate genus in Spain dating to the Middle Miocene era, roughly 12 million years ago. Nicknamed "Lluc," the male bears a strikingly "modern" facial appearance with a flat face, rather than a protruding one. The finding sheds important new light on the evolutionary development of hominids, including orangutans, chimpanzees, bonobos, gorillas and humans.
In a study appearing in the Proceedings of the National Academy of Sciences, Salvador Moyà-Solà, director of the Institut Català de Paleontologia (ICP) at the Universitat Autònoma de Barcelona, and colleagues present evidence for the new genus and species, dubbed Anoiapithecus brevirostris. The scientific name is derived from the region where the fossil was found (l’Anoia) and also from its "modern" facial morphology, characterized by a very short face.
The research team at the ICP also includes collaborator David M. Alba, predoctoral researcher Sergio Almécija, postdoctoral researcher Isaac Casanovas, researcher Meike Köhler, postdoctoral researcher Soledad De Esteban, collaborator Josep M. Robles, curator Jordi Galindo, and predoctoral researcher Josep Fortuny.
Their findings are based on a partial cranium that preserves most of the face and the associated mandible. The cranium was unearthed in 2004 in the fossil-rich area of Abocador de Can Mata (els Hostalets de Pierola, l’Anoia, Barcelona), where remains of other fossilized hominid species have been found. Preparing the fossil for study was a complicated process, due to the fragility of the remains. But once the material was available for analysis, the results were surprising: The specimen (IPS43000) combined a set of features that, until now, had never been found in the fossil record.
Anoiapithecus displays a very modern facial morphology, with a muzzle prognathism (i.e., protrusion of the jaw) so reduced that, within the family Hominidae, scientists can only find comparable values within the genus Homo, whereas the remaining great apes are notoriously more prognathic (i.e., having jaws that project forward markedly). The extraordinary resemblance does not indicate that Anoiapithecus has any relationship with Homo, the researchers note. However, the similarity might be a case of evolutionary convergence, where two species evolving separately share common features.
Lluc's discovery may also hold an important clue to the geographical origin of the hominid family. Some scientists have suspected that a group of primitive hominoids known as kenyapithecines (recorded from the Middle Miocene of Africa and Eurasia) might have been the ancestral group that all hominids came from. The detailed morphological study of the cranial remains of Lluc showed that, together with the modern anatomical features of hominids (e.g., nasal aperture wide at the base, high zygomatic rood, deep palate), it displays a set of primitive features, such as thick dental enamel, teeth with globulous cusps, very robust mandible and very procumbent premaxilla. These features characterize a group of primitive hominoids from the African Middle Miocene, known as afropithecids.
Interestingly, in addition to having a mixture of hominid and primitive afropithecid features, Lluc displays other characteristics, such as a very anterior position of the zygomatic, a very strong mandibular torus and, especially, a very reduced maxillary sinus. These are features shared with kenyapithecines believed to have dispersed outside the African continent and colonized the Mediterranean region, by about 15 million years ago.
In other words, the researchers speculate, hominids might have originally radiated in Eurasia from kenyapithecine ancestors of African origin. Later on, the ancestors of African great apes and humans would have dispersed again into Africa -- the so-called "into Africa" theory, which remains controversial. However, the authors do not completely rule out the possibility that pongines (orangutans and related forms) and hominines (African apes and humans) separately evolved in Eurasia and Africa, respectively, from different kenyapithecine ancestors.
The project at els Hostalets de Pierola is continuing and, the researchers anticipate, more fossil remains will be found in the future that will provide key information to test their hypotheses.
ScienceDaily (June 2, 2009) — Researchers have discovered a fossilized face and jaw from a previously unknown hominoid primate genus in Spain dating to the Middle Miocene era, roughly 12 million years ago. Nicknamed "Lluc," the male bears a strikingly "modern" facial appearance with a flat face, rather than a protruding one. The finding sheds important new light on the evolutionary development of hominids, including orangutans, chimpanzees, bonobos, gorillas and humans.
In a study appearing in the Proceedings of the National Academy of Sciences, Salvador Moyà-Solà, director of the Institut Català de Paleontologia (ICP) at the Universitat Autònoma de Barcelona, and colleagues present evidence for the new genus and species, dubbed Anoiapithecus brevirostris. The scientific name is derived from the region where the fossil was found (l’Anoia) and also from its "modern" facial morphology, characterized by a very short face.
The research team at the ICP also includes collaborator David M. Alba, predoctoral researcher Sergio Almécija, postdoctoral researcher Isaac Casanovas, researcher Meike Köhler, postdoctoral researcher Soledad De Esteban, collaborator Josep M. Robles, curator Jordi Galindo, and predoctoral researcher Josep Fortuny.
Their findings are based on a partial cranium that preserves most of the face and the associated mandible. The cranium was unearthed in 2004 in the fossil-rich area of Abocador de Can Mata (els Hostalets de Pierola, l’Anoia, Barcelona), where remains of other fossilized hominid species have been found. Preparing the fossil for study was a complicated process, due to the fragility of the remains. But once the material was available for analysis, the results were surprising: The specimen (IPS43000) combined a set of features that, until now, had never been found in the fossil record.
Anoiapithecus displays a very modern facial morphology, with a muzzle prognathism (i.e., protrusion of the jaw) so reduced that, within the family Hominidae, scientists can only find comparable values within the genus Homo, whereas the remaining great apes are notoriously more prognathic (i.e., having jaws that project forward markedly). The extraordinary resemblance does not indicate that Anoiapithecus has any relationship with Homo, the researchers note. However, the similarity might be a case of evolutionary convergence, where two species evolving separately share common features.
Lluc's discovery may also hold an important clue to the geographical origin of the hominid family. Some scientists have suspected that a group of primitive hominoids known as kenyapithecines (recorded from the Middle Miocene of Africa and Eurasia) might have been the ancestral group that all hominids came from. The detailed morphological study of the cranial remains of Lluc showed that, together with the modern anatomical features of hominids (e.g., nasal aperture wide at the base, high zygomatic rood, deep palate), it displays a set of primitive features, such as thick dental enamel, teeth with globulous cusps, very robust mandible and very procumbent premaxilla. These features characterize a group of primitive hominoids from the African Middle Miocene, known as afropithecids.
Interestingly, in addition to having a mixture of hominid and primitive afropithecid features, Lluc displays other characteristics, such as a very anterior position of the zygomatic, a very strong mandibular torus and, especially, a very reduced maxillary sinus. These are features shared with kenyapithecines believed to have dispersed outside the African continent and colonized the Mediterranean region, by about 15 million years ago.
In other words, the researchers speculate, hominids might have originally radiated in Eurasia from kenyapithecine ancestors of African origin. Later on, the ancestors of African great apes and humans would have dispersed again into Africa -- the so-called "into Africa" theory, which remains controversial. However, the authors do not completely rule out the possibility that pongines (orangutans and related forms) and hominines (African apes and humans) separately evolved in Eurasia and Africa, respectively, from different kenyapithecine ancestors.
The project at els Hostalets de Pierola is continuing and, the researchers anticipate, more fossil remains will be found in the future that will provide key information to test their hypotheses.
Friday, May 29, 2009
Virtual Reconstruction Of A Neanderthal Woman’s Birth Canal Reveals Insights Into Evolution Of Human Child Birth
http://www.sciencedaily.com/releases/2009/05/090528133423.htm
ScienceDaily (May 29, 2009) — Researchers from the University of California at Davis (USA) and the Max Planck Institute for Evolutionary Anthropology in Leipzig (Germany) present a virtual reconstruction of a female Neanderthal pelvis from Tabun (Israel).
Although the size of Tabun’s reconstructed birth canal shows that Neanderthal childbirth was about as difficult as in present-day humans, the shape indicates that Neanderthals retained a more primitive birth mechanism than modern humans. The virtual reconstruction of the pelvis from Tabun is going to be the first of its kind to be available for download on the internet for everyone interested in the evolution of humankind (PNAS, April 20th, 2009).
Childbirth in humans is more complicated than in other primates. Unlike the situation in great apes, human babies are about the same size as the birth canal, making passage difficult. The birth mechanism, a series of rotations the baby must undergo to successfully navigate its mother’s birth canal, distinguishes humans not only from great apes but also from lesser apes and monkeys.
It has been difficult to trace the evolution of human childbirth because the pelvic skeleton, which forms the margins of the birth canal, tends to survive poorly in the fossil record. Only three fossil female individuals preserve fairly complete birth canals, and they all date to earlier phases of human evolution.
Tim Weaver of the University of California (Davis, USA) and Jean-Jacques Hublin, director at the Max Planck Institute for Evolutionary Anthropology in Leipzig (Germany) now present a virtual reconstruction of a female Neanderthal pelvis from Tabun (Israel). The size of Tabun’s reconstructed birth canal shows that Neanderthal childbirth was about as difficult as in present-day humans. However, its shape indicates that Neanderthals retained a more primitive birth mechanism than modern humans, without rotation of the baby’s body.
A significant shift in childbirth apparently happened quite late in human evolution, during the last 400,000 - 300,000 years. Such a late shift underscores the uniqueness of human childbirth and the divergent evolutionary trajectories of Neanderthals and the lineage leading to present-day humans.
The virtual reconstruction of the pelvis from Tabun is going to be the first of its kind to be available for download on the internet for everyone interested in human evolution. The computer files will be available from the websites of University of California at Davis and the Max Planck Institute for Evolutionary Anthropology.
ScienceDaily (May 29, 2009) — Researchers from the University of California at Davis (USA) and the Max Planck Institute for Evolutionary Anthropology in Leipzig (Germany) present a virtual reconstruction of a female Neanderthal pelvis from Tabun (Israel).
Although the size of Tabun’s reconstructed birth canal shows that Neanderthal childbirth was about as difficult as in present-day humans, the shape indicates that Neanderthals retained a more primitive birth mechanism than modern humans. The virtual reconstruction of the pelvis from Tabun is going to be the first of its kind to be available for download on the internet for everyone interested in the evolution of humankind (PNAS, April 20th, 2009).
Childbirth in humans is more complicated than in other primates. Unlike the situation in great apes, human babies are about the same size as the birth canal, making passage difficult. The birth mechanism, a series of rotations the baby must undergo to successfully navigate its mother’s birth canal, distinguishes humans not only from great apes but also from lesser apes and monkeys.
It has been difficult to trace the evolution of human childbirth because the pelvic skeleton, which forms the margins of the birth canal, tends to survive poorly in the fossil record. Only three fossil female individuals preserve fairly complete birth canals, and they all date to earlier phases of human evolution.
Tim Weaver of the University of California (Davis, USA) and Jean-Jacques Hublin, director at the Max Planck Institute for Evolutionary Anthropology in Leipzig (Germany) now present a virtual reconstruction of a female Neanderthal pelvis from Tabun (Israel). The size of Tabun’s reconstructed birth canal shows that Neanderthal childbirth was about as difficult as in present-day humans. However, its shape indicates that Neanderthals retained a more primitive birth mechanism than modern humans, without rotation of the baby’s body.
A significant shift in childbirth apparently happened quite late in human evolution, during the last 400,000 - 300,000 years. Such a late shift underscores the uniqueness of human childbirth and the divergent evolutionary trajectories of Neanderthals and the lineage leading to present-day humans.
The virtual reconstruction of the pelvis from Tabun is going to be the first of its kind to be available for download on the internet for everyone interested in human evolution. The computer files will be available from the websites of University of California at Davis and the Max Planck Institute for Evolutionary Anthropology.
Male Or Female? Coloring Provides Gender Cues
http://www.sciencedaily.com/releases/2009/05/090527121049.htm
ScienceDaily (May 28, 2009) — Our brain is wired to identify gender based on facial cues and coloring, according to a new study published in the Journal of Vision. Psychology Professor Frédéric Gosselin and his Université de Montréal team found the luminescence of the eyebrow and mouth region is vital in rapid gender discrimination.
"As teenagers, dimorphism (systematic difference between sexes) increases in the nose, chin, mouth, jaw, eyes and general shape of faces," says Nicolas Dupuis-Roy, lead author of the study. "Yet we aren't conscious of how our brain recognizes those differences."
To discover those reference points, Dupuis-Roy and colleagues showed photos of 300 Caucasian faces to some 30 participants. Subjects were asked to identify gender based on images where parts of faces were concealed using a technology called Bubbles.
The investigation found that eyes and mouths, specifically their subtle shading or luminance, are paramount in identifying gender. Unlike previous studies, which found the gap between the eyelid and eyebrow as essential in gender ID, this investigation found the shades of reds and greens around mouths and eyes led to faster gender discrimination.
"Studies have shown that an androgynous face is considered male if the skin complexion is redder, and considered female if the complexion is greener," says Dupuis-Roy. "However, it is the opposite for the mouth. A woman's mouth is usually redder. Our brain interprets this characteristic as female."
"A man's face usually reflects less light around the eyebrows. This is because they are usually thicker. The same applies to the upper lip and chin, which are hairier areas," he adds, noting people clearly use colour to rapidly identify gender.
This research was supported by the Fonds québécois de la recherche sur la nature et les technologies and Natural Sciences and Engineering Research Council of Canada. PhD student Isabelle Fortin and Professor Daniel Fiset also participated in the study.
ScienceDaily (May 28, 2009) — Our brain is wired to identify gender based on facial cues and coloring, according to a new study published in the Journal of Vision. Psychology Professor Frédéric Gosselin and his Université de Montréal team found the luminescence of the eyebrow and mouth region is vital in rapid gender discrimination.
"As teenagers, dimorphism (systematic difference between sexes) increases in the nose, chin, mouth, jaw, eyes and general shape of faces," says Nicolas Dupuis-Roy, lead author of the study. "Yet we aren't conscious of how our brain recognizes those differences."
To discover those reference points, Dupuis-Roy and colleagues showed photos of 300 Caucasian faces to some 30 participants. Subjects were asked to identify gender based on images where parts of faces were concealed using a technology called Bubbles.
The investigation found that eyes and mouths, specifically their subtle shading or luminance, are paramount in identifying gender. Unlike previous studies, which found the gap between the eyelid and eyebrow as essential in gender ID, this investigation found the shades of reds and greens around mouths and eyes led to faster gender discrimination.
"Studies have shown that an androgynous face is considered male if the skin complexion is redder, and considered female if the complexion is greener," says Dupuis-Roy. "However, it is the opposite for the mouth. A woman's mouth is usually redder. Our brain interprets this characteristic as female."
"A man's face usually reflects less light around the eyebrows. This is because they are usually thicker. The same applies to the upper lip and chin, which are hairier areas," he adds, noting people clearly use colour to rapidly identify gender.
This research was supported by the Fonds québécois de la recherche sur la nature et les technologies and Natural Sciences and Engineering Research Council of Canada. PhD student Isabelle Fortin and Professor Daniel Fiset also participated in the study.
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