Marc Verha
Thu, Jun-21-07, 17:17
http://notexactlyrocketscience.wordpress.com/2007/06/18/inner-
-ear-size-can-p redict-a-mammal%E2%80%99s-agility/
10.1073/pnas.0704250104 OPEN ACCESS ARTICLE The primate
semicircular canal system and locomotion Fred Spoor,
Theodore Garland Jr, Gail Krovitz, Timothy M Ryan,
Mary T Silcox & Alan Walker 2007
The semicircular canal system of vertebrates helps coordinate
body movements, including stabilization of gaze during
locomotion. Quantitative phylogenetically informed analysis of
the radius of curvature of the three semicircular canals in 91
extant and recently extinct primate species and 119 other
mammalian taxa provide support for the hypothesis that canal
size varies in relation to the jerkiness of head motion during
locomotion. Primate and other mammalian species studied here
that are agile and have fast, jerky locomotion have
significantly larger canals relative to body mass than those
that move more cautiously.
From the discussion: ... The strong relationship between
SCC.size & locomotor agility is clearly evident in a variety
of primate groups. The leaping tarsiers & galagos have large
canals relative to their body size, whereas the slow
quadrupedal lorises, although of similar body size, lie on the
lower end of the distribution with relatively small canals. At
larger body masses, this relationship also holds. The
acrobatic brachiating gibbons have rel.large canals for their
body size, compared with the great apes. The sloth lemurs &
koala lemurs have small canals for their body size, and
Palaeopropithecus in particular has very small canals to match
its reconstructed extremely slow locomotion. (Some or all of
these subfossil large Madagascan fossils may have been
aquarboreal. --MV) In some cases, canal size does not seem to
match expectations based on the locomotor behavioral
classification. This could occur when a small,
unrepresentative sample falls toward the margins of a speciesı
morphological range of variation, especially when combined
with a less secure estimate of body mass. It may also be that
locomotor behavior was misclassified because certain aspects
critical to the perception of angular rather than linear
motion were not recognized. A possible example is Ateles
geoffroyi, which is classified as medium in agility, but its
rather large canals fit well with its acrobatic behavior.
Importantly, the 3 canals do not necessarily express locomotor
behavior in equal measure, because this may depend on the
planes of head motion involved. For example, during hominin
evolution only the anterior & posterior canals enlarge with
the emergence of modern-human-like bipedal locomotion (2). In
contrast, tarsiers & galagos on the one hand, and lorises on
the other are most distinct in lateral canal size. Likewise,
the small lateral canal of Alouatta seniculus is consistent
with its less agile behavior. However, its anterior canal
appears unexpectedly large, possibly the consequence of
spatial constraints of the subarcuate fossa (24), which opens
into the endocranial cavity through the arc of the anterior
canal, and houses a lobule of the cerebellum. In all, the
species that most strikingly seem to contrast with the overall
canalagility correlation are the 4 callitrichids. These are
classified as agile, but their anterior & lateral canals fall
between the middle & lower end of the canal size distribution.
It is unclear why this is, and more work will need to be done
to understand the factors underlying this exceptional
morphology. In nearly all cases, the phylogenetic GLS models
employing some type of branch length transformation
outperformed both the star phylogeny (conventional regression)
and the GLS method by using untransformed divergence times
gathered from the literature. Of the 3 branch length
transformations used, Grafenıs & Pagelıs typically performed
best. The addition of well dated extinct species throughout
our phylogenetic tree will result in more accurate
reconstructions of the ancestral nodes, which in turn may then
allow a better reconstruction of the evolution of characters.
Nevertheless, as was found here, transformed trees may still
perform better than those based on divergence times. This may
be for a variety of reasons, including the presence of
unavoidable measurement error in the estimates of speciesı
mean BM and canal radii (25). The similarity of results
between the conventional and the phylogenetic regression
models indicates that the SCC system holds a very strong
functional signal related to head motion & locomotor agility.
Such an apparently robust functional relationship across
primates & other mammals suggests that adjusting arc size, and
thus endolymph circuit length, constitutes a prime adaptive
mechanism of how the canal system is tuned to the kinematic
characteristics of different locomotor repertoires. This
finding will contribute to a more fundamental understanding of
the biomechanics of the canal system. On a more practical
level, it confirms the potential utility of the SCCs for the
reconstruction of behavior from fossil specimens.
From suppl.text: ... 86 Ma for Primates/Scandentia-Dermoptera
(Springer et al.). ... 77 Ma for Strepsi/Haplorhine split ...
The base of Strepsirrhines at 69 Ma (Yoder & Yang) the base of
Lorisiformes at 55 Ma, the base of Lemuriformes at 62.7 ...
Afr./As.lorises was set at 42 Ma ...
Galagoides/Galago-Otolemur clade was set to 30 Ma The base of
the Haplorhines was set at 55 Ma (Ross et al.) based on the
presence of Tarsius eocaenus at 45 Ma. ... platy/catarrhine is
placed at 43.6 Ma (Eizirik et al.). The base of the
platyrrhine radiation is set at 25 Ma based on the initial
appearance of platyrrhines in the fossil record during the
early Mio. The presence in the Miocene of fossils purported to
belong to modern clades suggests a rapid radiation of known
clades after 25 mya.
... cercopith/hominoid split was placed at 34.7 Ma (Yoder &
Yang), which is similar to other estimates (15). The phylogeny
of hylobatids was based on Roos & Geissmann, & the divergence
dates were arbitrary following the 15 Ma split with hominids
(sensu hominids+pongids --MV). The divergence dates within
hominids were based on Stauffer et al. ...
> Reconstructing The Biology Of Extinct Species: A New
> Approach Science Daily http://www.sciencedaily.com/releases-
> /2007/06/070618174733.htm
>
> An international research team has documented the link
> between the way an animal moves and the dimensions of an
> important part of its organ of balance, the three
> semicircular canals of the inner ear on each side of the
> skull. "We have shown that there is a fundamental adaptive
> mechanism linking a species' locomotion with the sensory
> systems that process information about its environment,"
> says Alan Walker, Evan Pugh Professor of Anthropology and
> Biology at Penn State University, one of the team's leaders.
>
> A computer reconstruction of an adult female baboon skull
> from high-resolution X-ray computed tomography (CT) slices.
> The skull is rendered transparent to show the position of
> the three semicircular canals and cochlea of left inner ear
> filled in red. The enlargement of the canals and cochlea is
> five times the size of the canals shown in the skull. Each
> canal is approximately 5 mm in diameter. (Credit: Alan
> Walker lab, Penn State)
>
> The researchers studied 91 separate primate species,
> including all taxonomic families. The study also included
> 119 additional species, most of which are mammals ranging in
> size from mouse to elephant, that habitually move in diverse
> ways in varied environments.
>
> The project is the first large-scale study to document the
> relationship of the dimensions of the semicircular canals to
> locomotion. These structures are filled with a fluid, which
> moves within the canals when the animal moves. The fluid's
> movement is sensed by special cells that send signals to the
> brain, triggering the neck and eye muscles to reflexively
> keep the visual image stable.
>
> The basic hypothesis of the project was that the organ of
> balance -- which helps stabilize an animal's gaze and
> coordinate its movements as it travels through the
> environment -- should be irrevocably linked to the type of
> locomotion produced by its limbs. "If an animal evolves a
> new way of moving about the world, its organ of balance must
> evolve accordingly," Walker explains. From the visual
> information, the animal tracks its position relative to
> stationary objects such as tree trunks, branches, rocks or
> cliffs, or the ground. Having a stable image of the
> environment is especially crucial for acrobatic animals that
> leap, glide, or fly.
>
> To make the discovery, the scientists scanned skull samples
> of each species, measuring the size of each semicircular
> canal and calculating the radius of curvature. Most of the
> specimens were scanned at the Center for Quantitative
> Imaging at Penn State on the OMNI-X high-resolution x-ray CT
> scanner, which can resolve features approximately 1/100 the
> size of those detected by medical CT scanners. In addition,
> experienced field workers used personal knowledge or film of
> animals in the wild to classify species into one of six
> locomotor categories ranging from very slow and deliberate
> to fast and agile. The scientists then compared the canal
> size of each species to its category of movement.
>
> The results revealed a highly significant statistical
> relationship between the radius of curvature of the
> semicircular canals and the species' habitual way of moving.
> More acrobatic species consistently have semicircular canals
> with a larger radius of curvature than do slower-moving
> ones. For example, a small, fast-moving leaper like a
> bushbaby has semicircular canals that are relatively and
> absolutely much bigger than those of the similar-sized,
> slow-moving loris.
>
> However, because larger animals have absolutely larger
> canals, the analysis had to take body size into account.
> The research revealed that this functional tie between
> the semicircular canals and locomotor pattern is evident
> both within the primates alone and within the entire
> mammalian sample.
>
> "How an animal moves is a basic adaptation," says Walker, an
> expert in primate locomotion. "Now we have a way to
> reconstruct how extinct species moved that is completely
> independent of analysis of the limb structure. For the first
> time, we can test our previous conclusions using a new
> source of information."
>
> Co-leader of the team was Fred Spoor, Professor of Anatomy
> at University College, London. Spoor originally studied a
> small number of species for his doctoral research and
> suggested conducting a detailed investigation using modern
> techniques. Other researchers on the project were Professor
> of Biology Theodore Garland Jr. of the University of
> California, Riverside; Senior Instructional Design
> Consultant Gail Krovitz, of the eCollege company; Research
> Associate in Anthropology Timothy M. Ryan of Penn State
> University; and Associate Professor of Anthropology Mary T.
> Silcox of the University of Winnipeg in Canada.
>
> The team's article on its research will be published on 26
> June in the print edition of the Proceedings of the National
> Academy of Sciences and in the journal's online early
> edition during the week of 18 to 22 June. The research
> received financial support from the National Science
> Foundation
-ear-size-can-p redict-a-mammal%E2%80%99s-agility/
10.1073/pnas.0704250104 OPEN ACCESS ARTICLE The primate
semicircular canal system and locomotion Fred Spoor,
Theodore Garland Jr, Gail Krovitz, Timothy M Ryan,
Mary T Silcox & Alan Walker 2007
The semicircular canal system of vertebrates helps coordinate
body movements, including stabilization of gaze during
locomotion. Quantitative phylogenetically informed analysis of
the radius of curvature of the three semicircular canals in 91
extant and recently extinct primate species and 119 other
mammalian taxa provide support for the hypothesis that canal
size varies in relation to the jerkiness of head motion during
locomotion. Primate and other mammalian species studied here
that are agile and have fast, jerky locomotion have
significantly larger canals relative to body mass than those
that move more cautiously.
From the discussion: ... The strong relationship between
SCC.size & locomotor agility is clearly evident in a variety
of primate groups. The leaping tarsiers & galagos have large
canals relative to their body size, whereas the slow
quadrupedal lorises, although of similar body size, lie on the
lower end of the distribution with relatively small canals. At
larger body masses, this relationship also holds. The
acrobatic brachiating gibbons have rel.large canals for their
body size, compared with the great apes. The sloth lemurs &
koala lemurs have small canals for their body size, and
Palaeopropithecus in particular has very small canals to match
its reconstructed extremely slow locomotion. (Some or all of
these subfossil large Madagascan fossils may have been
aquarboreal. --MV) In some cases, canal size does not seem to
match expectations based on the locomotor behavioral
classification. This could occur when a small,
unrepresentative sample falls toward the margins of a speciesı
morphological range of variation, especially when combined
with a less secure estimate of body mass. It may also be that
locomotor behavior was misclassified because certain aspects
critical to the perception of angular rather than linear
motion were not recognized. A possible example is Ateles
geoffroyi, which is classified as medium in agility, but its
rather large canals fit well with its acrobatic behavior.
Importantly, the 3 canals do not necessarily express locomotor
behavior in equal measure, because this may depend on the
planes of head motion involved. For example, during hominin
evolution only the anterior & posterior canals enlarge with
the emergence of modern-human-like bipedal locomotion (2). In
contrast, tarsiers & galagos on the one hand, and lorises on
the other are most distinct in lateral canal size. Likewise,
the small lateral canal of Alouatta seniculus is consistent
with its less agile behavior. However, its anterior canal
appears unexpectedly large, possibly the consequence of
spatial constraints of the subarcuate fossa (24), which opens
into the endocranial cavity through the arc of the anterior
canal, and houses a lobule of the cerebellum. In all, the
species that most strikingly seem to contrast with the overall
canalagility correlation are the 4 callitrichids. These are
classified as agile, but their anterior & lateral canals fall
between the middle & lower end of the canal size distribution.
It is unclear why this is, and more work will need to be done
to understand the factors underlying this exceptional
morphology. In nearly all cases, the phylogenetic GLS models
employing some type of branch length transformation
outperformed both the star phylogeny (conventional regression)
and the GLS method by using untransformed divergence times
gathered from the literature. Of the 3 branch length
transformations used, Grafenıs & Pagelıs typically performed
best. The addition of well dated extinct species throughout
our phylogenetic tree will result in more accurate
reconstructions of the ancestral nodes, which in turn may then
allow a better reconstruction of the evolution of characters.
Nevertheless, as was found here, transformed trees may still
perform better than those based on divergence times. This may
be for a variety of reasons, including the presence of
unavoidable measurement error in the estimates of speciesı
mean BM and canal radii (25). The similarity of results
between the conventional and the phylogenetic regression
models indicates that the SCC system holds a very strong
functional signal related to head motion & locomotor agility.
Such an apparently robust functional relationship across
primates & other mammals suggests that adjusting arc size, and
thus endolymph circuit length, constitutes a prime adaptive
mechanism of how the canal system is tuned to the kinematic
characteristics of different locomotor repertoires. This
finding will contribute to a more fundamental understanding of
the biomechanics of the canal system. On a more practical
level, it confirms the potential utility of the SCCs for the
reconstruction of behavior from fossil specimens.
From suppl.text: ... 86 Ma for Primates/Scandentia-Dermoptera
(Springer et al.). ... 77 Ma for Strepsi/Haplorhine split ...
The base of Strepsirrhines at 69 Ma (Yoder & Yang) the base of
Lorisiformes at 55 Ma, the base of Lemuriformes at 62.7 ...
Afr./As.lorises was set at 42 Ma ...
Galagoides/Galago-Otolemur clade was set to 30 Ma The base of
the Haplorhines was set at 55 Ma (Ross et al.) based on the
presence of Tarsius eocaenus at 45 Ma. ... platy/catarrhine is
placed at 43.6 Ma (Eizirik et al.). The base of the
platyrrhine radiation is set at 25 Ma based on the initial
appearance of platyrrhines in the fossil record during the
early Mio. The presence in the Miocene of fossils purported to
belong to modern clades suggests a rapid radiation of known
clades after 25 mya.
... cercopith/hominoid split was placed at 34.7 Ma (Yoder &
Yang), which is similar to other estimates (15). The phylogeny
of hylobatids was based on Roos & Geissmann, & the divergence
dates were arbitrary following the 15 Ma split with hominids
(sensu hominids+pongids --MV). The divergence dates within
hominids were based on Stauffer et al. ...
> Reconstructing The Biology Of Extinct Species: A New
> Approach Science Daily http://www.sciencedaily.com/releases-
> /2007/06/070618174733.htm
>
> An international research team has documented the link
> between the way an animal moves and the dimensions of an
> important part of its organ of balance, the three
> semicircular canals of the inner ear on each side of the
> skull. "We have shown that there is a fundamental adaptive
> mechanism linking a species' locomotion with the sensory
> systems that process information about its environment,"
> says Alan Walker, Evan Pugh Professor of Anthropology and
> Biology at Penn State University, one of the team's leaders.
>
> A computer reconstruction of an adult female baboon skull
> from high-resolution X-ray computed tomography (CT) slices.
> The skull is rendered transparent to show the position of
> the three semicircular canals and cochlea of left inner ear
> filled in red. The enlargement of the canals and cochlea is
> five times the size of the canals shown in the skull. Each
> canal is approximately 5 mm in diameter. (Credit: Alan
> Walker lab, Penn State)
>
> The researchers studied 91 separate primate species,
> including all taxonomic families. The study also included
> 119 additional species, most of which are mammals ranging in
> size from mouse to elephant, that habitually move in diverse
> ways in varied environments.
>
> The project is the first large-scale study to document the
> relationship of the dimensions of the semicircular canals to
> locomotion. These structures are filled with a fluid, which
> moves within the canals when the animal moves. The fluid's
> movement is sensed by special cells that send signals to the
> brain, triggering the neck and eye muscles to reflexively
> keep the visual image stable.
>
> The basic hypothesis of the project was that the organ of
> balance -- which helps stabilize an animal's gaze and
> coordinate its movements as it travels through the
> environment -- should be irrevocably linked to the type of
> locomotion produced by its limbs. "If an animal evolves a
> new way of moving about the world, its organ of balance must
> evolve accordingly," Walker explains. From the visual
> information, the animal tracks its position relative to
> stationary objects such as tree trunks, branches, rocks or
> cliffs, or the ground. Having a stable image of the
> environment is especially crucial for acrobatic animals that
> leap, glide, or fly.
>
> To make the discovery, the scientists scanned skull samples
> of each species, measuring the size of each semicircular
> canal and calculating the radius of curvature. Most of the
> specimens were scanned at the Center for Quantitative
> Imaging at Penn State on the OMNI-X high-resolution x-ray CT
> scanner, which can resolve features approximately 1/100 the
> size of those detected by medical CT scanners. In addition,
> experienced field workers used personal knowledge or film of
> animals in the wild to classify species into one of six
> locomotor categories ranging from very slow and deliberate
> to fast and agile. The scientists then compared the canal
> size of each species to its category of movement.
>
> The results revealed a highly significant statistical
> relationship between the radius of curvature of the
> semicircular canals and the species' habitual way of moving.
> More acrobatic species consistently have semicircular canals
> with a larger radius of curvature than do slower-moving
> ones. For example, a small, fast-moving leaper like a
> bushbaby has semicircular canals that are relatively and
> absolutely much bigger than those of the similar-sized,
> slow-moving loris.
>
> However, because larger animals have absolutely larger
> canals, the analysis had to take body size into account.
> The research revealed that this functional tie between
> the semicircular canals and locomotor pattern is evident
> both within the primates alone and within the entire
> mammalian sample.
>
> "How an animal moves is a basic adaptation," says Walker, an
> expert in primate locomotion. "Now we have a way to
> reconstruct how extinct species moved that is completely
> independent of analysis of the limb structure. For the first
> time, we can test our previous conclusions using a new
> source of information."
>
> Co-leader of the team was Fred Spoor, Professor of Anatomy
> at University College, London. Spoor originally studied a
> small number of species for his doctoral research and
> suggested conducting a detailed investigation using modern
> techniques. Other researchers on the project were Professor
> of Biology Theodore Garland Jr. of the University of
> California, Riverside; Senior Instructional Design
> Consultant Gail Krovitz, of the eCollege company; Research
> Associate in Anthropology Timothy M. Ryan of Penn State
> University; and Associate Professor of Anthropology Mary T.
> Silcox of the University of Winnipeg in Canada.
>
> The team's article on its research will be published on 26
> June in the print edition of the Proceedings of the National
> Academy of Sciences and in the journal's online early
> edition during the week of 18 to 22 June. The research
> received financial support from the National Science
> Foundation