THE EVOLUTIONARY HISTORY OF CETACEAN BRAIN AND BODY SIZE: CETACEAN BRAIN EVOLUTION

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The consensus is that large brain size is evidence of, or necessary for, the behavioral complexity and cognitive abilities observed in cetaceans.

“Although noncognitive hypotheses have been proposed to explain the large brains of odontocetes (Manger 2006), the consensus is that large brain size is evidence of, or necessary for, the behavioral complexity and cognitive abilities observed in cetaceans (Marino 2002;Simmonds 2006;Connor 2007;Marino et al. 2007).”

• cites Marino 2002 sourceNot checked — no full text of the source
• cites Simmonds 2006 sourceNot checked — no full text of the source
• cites Connor 2007 sourcePartly supported

  The Abstract (page unavailable) links complex dolphin alliances to potential cognitive demands and says social competition selected for greater cognitive abilities and large brain size. The Introduction (page unavailable) presents social competition as a hypothesis that may best explain extreme brain size, not as a consensus; the copy also does not establish that a large brain is necessary for the observed abilities. (LLM, conf=0.82)

  Experimental — accuracy not yet measured

May combine two claims.

In contrast to cetaceans, primate evolution has been characterized by a directional trend in brain mass, but not body mass, resulting in a strong trend toward increasing relative brain size.

“In contrast to cetaceans, primate evolution has been characterized by a directional trend in brain mass, but not body mass, resulting in a strong trend toward increasing relative brain size (Montgomery et al. 2010).”

• cites Montgomery et al. 2010 sourceSupported

Classified as probably not a substantial claim. May combine two claims.

Increases in relative brain size are almost ubiquitous across the primate tree and are produced by directional evolution of increased brain mass in a background of body mass evolution that shows no significant trend to increase through time.

“Increases in relative brain size are almost ubiquitous across the primate tree and are produced by directional evolution of increased brain mass in a background of body mass evolution that shows no significant trend to increase through time (Montgomery et al. 2010).”

• cites Montgomery et al. 2010 sourceSupported

May combine two claims.

Cetacean brain:body allometry is predominantly altered during three key periods (the origin of crown cetaceans, the origin of odontocetes, and the origin of mysticetes), whereas primate brain and body mass evolved under contrasting selective regimes across longer periods of time resulting in a continuous allometric change and the expansion of relative brain size.

“Whereas cetacean brain:body allometry is predominantly altered during three key periods (the origin of crown cetaceans, the origin of odontocetes, and the origin of mysticetes), primate brain and body mass evolved under contrasting selective regimes across longer periods of time resulting in a continuous allometric change and the expansion of relative brain size (Montgomery et al. 2010).”

• cites Montgomery et al. 2010 sourcePartly supported

  Split into 2 atoms — 0 confirmed, 1 partially supported, 0 disputed, 0 misattributed, 1 unverifiable. Expand the claim to see per-atom verdicts.

  Experimental — accuracy not yet measured

Probably not a substantial claim: may not pass S3 (load-bearing).

A trade-off between relative brain size and the amount of adipose depots has recently been demonstrated across mammals.

“Similarly, a trade-off between relative brain size and the amount of adipose depots has recently been demonstrated across mammals (Navarrete et al. 2011).”

• cites Navarrete et al. 2011 sourceSupported

May combine two claims.

Social communication and structure are often complex in mysticetes, and include long-term social bonds, long-range communication, cooperative hunting, cultural traditions, and fission-fusion like social behavior.

“The available information suggests, however, that social communication and structure are often complex in mysticetes, and include long-term social bonds, long-range communication, cooperative hunting, cultural traditions, and fission-fusion like social behavior (Simmonds 2006;Marino et al. 2007;Whitehead 2011).”

• cites Simmonds 2006 sourceNot checked — no full text of the source
• cites Marino et al. 2007 sourcePartly supported

  In “Cetacean Cognition and Behavior in the Wild” (page not supplied), the paper identifies cultural traditions in humpback whales and describes mysticetes as low-frequency sound producers. But its examples of long-term bonds, cooperative group hunting, and fission-fusion society concern dolphins or killer whales, not mysticetes; it also does not establish long-range communication specifically. (LLM, conf=0.87)

  Experimental — accuracy not yet measured
• cites Whitehead 2011Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

Primates show a strong directional trend for relative brain size to increase through time whereas cetaceans do not.

“First, primates show a strong directional trend for relative brain size to increase through time (Montgomery et al. 2010) whereas cetaceans do not.”

• cites Montgomery et al. 2010 sourceSupported

Classified as probably not a substantial claim.

This trade-off is postulated to be due to locomotor constraints associated with carrying fat depots conflicting with the need for fat storage as a means of surviving periods of low food availability.

“This trade-off is postulated to be due to locomotor constraints associated with carrying fat depots conflicting with the need for fat storage as a means of surviving periods of low food availability.”

• cites Navarrete et al. 2011 sourceSupported

May combine two claims.

Both mysticete and odontocete clades possess a highly expanded and convoluted cortex and cerebellum, suggesting that either major structural changes occurred in parallel in mysticetes and odontocetes or that these changes occurred before the origin of crown Cetacea.

“both clades possess a highly expanded and convoluted cortex and cerebellum suggesting that either major structural changes occurred in parallel in mysticetes and odontocetes or that these changes occurred before the origin of crown Cetacea (Marino et al. 2000;Oelschläger and Oelschläger 2002;Marino 2004;Tartarelli and Bisconti 2006;Hof and van der Gucht 2007).”

• cites Marino et al. 2000 sourceCould not verify

  Split into 2 atoms — 0 confirmed, 0 partially supported, 0 disputed, 0 misattributed, 2 unverifiable. Expand the claim to see per-atom verdicts.

  Experimental — accuracy not yet measured
• cites Oelschläger and Oelschläger 2002Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Marino 2004Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

May combine two claims.

Recent studies point toward brain and body mass having independent genetic bases and different aspects of brain development evolving independently, suggesting selection can act on brain size and structure, or body mass, without causing correlated shifts in the other.

“Recent studies point toward brain and body mass having independent genetic bases and different aspects of brain development evolving independently (Barton and Capellini 2011;Montgomery et al. 2011;Hager et al. 2012), suggesting selection can act on brain size and structure, or body mass, without causing correlated shifts in the other.”

• cites Barton and Capellini 2011 sourceNot checked — no full text of the source
• cites Montgomery et al. 2011 sourceNot checked — no full text of the source
• cites Hager et al. 2012 sourceSupported

May combine two claims.

The most basal node in Cetacea had an estimated brain mass of 308.738 g, a 4.32-fold increase.

“Brain mass is estimated to be 308.738g (95% CI = 308.074-309.404g), a 4.32-fold increase, giving an EQ of 0.371”

May combine two claims.

The most basal node in Cetacea had an estimated body mass of 541.330 kg, within the range of extant odontocetes and over a 10-fold increase relative to the common ancestor of hippos and whales.

“It is estimated to have had a body mass of 541.330 kg (95% confidence interval [CI] = 539.181-543.487kg), within the range of extant odontocetes and representing over a 10-fold increase in body mass relative to the common ancestor of hippos and whales”

May combine two claims.

The rate of increase in EQ along the terminal Homo lineage is exceeded by three primate and four cetacean branches, with the terminal T. truncatus branch having the highest rate.

“The rate of increase in EQ along the terminal Homo lineage is exceeded by three primate and four cetacean branches; with the terminal T. truncatus branch having the highest rate.”

May combine two claims.

During the descent of P. macrocephalus, brain mass increased by only 6.5-fold, leading to a decrease in EQ from 2.022 to 0.575.

“During the descent of P. macrocephalus, brain mass increased by only 6.5-fold, leading to a decrease in EQ from 2.022 (95% CI = 2.009-2.035g) to 0.575.”

May combine two claims.

During this period, brain mass remained relatively constant between 520 and 540 g, and EQ climbed steadily from 1.383 to 2.146.

“During this period, brain mass remained relatively constant, between 520 and 540 g, and as a result, EQ climbed steadily from 1.383 to 2.146 (node 22; 95% CI = 2.135-2.157).”

May combine two claims.

The frequency of decreases in brain mass and EQ is much greater in cetaceans, whereas the frequency of body mass decreases is greater in primates.

“The frequency of decreases in brain mass and EQ is much greater in cetaceans, whereas the frequency of body mass decreases is greater in primates.”

May combine two claims.

Large proportional increases in EQ are observed on the stem lineage to crown Cetacea, on the stem to crown Odontoceti, and on terminal branches leading to Lagenorhynchus albirostris and Globicephala macrorhynchus.

“Large proportional increases in EQ are observed on the stem lineage to crown Cetacea (nodes 1-9: 0.454-1.383),on the stem to crown Odontoceti (nodes 9-22: 1.383-2.146),and on the terminal branches leading to Lagenorhynchus albirostris and Globicephala macrorhynchus, both of which show very little change in brain mass.”

May combine two claims.

No mysticete branch is estimated to have experienced a decrease in brain or body mass, whereas 7 of 11 branches show decreases in EQ.

“No branch is estimated to have experienced a decrease in brain or body mass, whereas 7 of 11 branches show decreases in EQ.”

May combine two claims.

Orcinus orca shows a 5.3-fold increase in brain mass, which together with its large body size leads to a decrease in EQ from 3.867 to 2.764.

“Orcinus orca shows a 5.3-fold increase in brain mass, which together with its large body size also leads to a decrease in EQ from 3.867 (95% CI = 3.851-3.883)to 2.764.”

May combine two claims.

The ancestral odontocete had an estimated brain mass of 539.533 g, within the 95% CIs for the estimate at node 9.

“Brain mass is estimated to have been 539.533g (95% CI = 538.282-549.787g), within the 95% CIs for the estimate at node 9.”

May combine two claims.

The origin of extant mysticetes from the last common ancestor of crown Cetacea was accompanied by a doubling of brain mass but a 16-fold increase in body mass, resulting in decreased EQ.

“The origin of extant mysticetes from the last common ancestor of crown Cetacea (between nodes 9 and 10) is therefore accompanied by a doubling of brain mass but more notably a 16-fold increase in body mass resulting in a decreased EQ.”

May combine two claims.

The ancestral odontocete (node 15) had an estimated body mass of 130.472 kg, a 22% decrease from the ancestral crown cetacean (node 9).

“The ancestral odontocete (node 15) had an estimated body mass of 130.472 kg (95% CI = 129.927-131.022kg), a decrease in body mass of 22% from the ancestral crown cetacean (node 9).”

May combine two claims.

The distribution of EQ values across cetaceans is dominated by a major decrease on the stem to crown Mysticeti and a major increase on the stem to crown Odontoceti, in both cases driven by changes in body mass.

“the distribution of EQ values across cetaceans is dominated by a major decrease on the stem to crown Mysticeti and a major increase on the stem to crown Odontoceti, in both cases driven by changes in body mass.”

May combine two claims.

The expectation that relative brain size tends to increase through time in mammals is not met in Cetacea as a whole, or within Odontoceti.

“The expectation that relative brain size tends to increase through time in mammals (Jerison 1973;Gould 1988) is not met in Cetacea as a whole, or within Odontoceti.”

• cites Jerison 1973Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Gould 1988 sourceNot checked — no full text of the source

May combine two claims.

Both mysticetes and odontocetes show similar patterns of body and brain mass evolution, with both traits generally increasing through time.

“Despite large differences in EQ, both mysticetes and odontocetes show similar patterns of body and brain mass evolution, with both traits generally increasing through time.”

May combine two claims.

Cetaceans rival primates in brain size relative to body size and include species with the largest brains and biggest bodies to have ever evolved.

“Cetaceans rival primates in brain size relative to body size and include species with the largest brains and biggest bodies to have ever evolved.”

• cites Marino 1998 sourceNot checked — no full text of the source

May combine two claims.

The most basal node in Cetacea included in the phylogeny was probably predominantly aquatic but capable of some terrestrial locomotion.

“The most basal node in Cetacea included in our phylogeny (node 2) was probably predominantly aquatic but, like Dalanistes and Rodhocetus (Gingerich 2003), capable of some terrestrial locomotion.”

• cites Gingerich 2003 sourceNot checked — no full text of the source

May combine two claims.

There is evidence linking whole brain size to cognitive performance and survival in novel environments.

“Yet, despite being a somewhat crude measure, there is evidence linking whole brain size to cognitive performance (Deaner et al. 2007;Reader et al. 2011) and survival in novel environments (Sol et al. 2008).”

• cites Deaner et al. 2007 sourceNot checked — no full text of the source
• cites Reader et al. 2011 sourceNot checked — no full text of the source
• cites Sol et al. 2008 sourceNot checked — no full text of the source

May combine two claims.

Data on ECV and brain mass from the same species showed negligible differences, with the slope not significantly different from one and the intercept not significantly different from zero.

“Data on ECV and brain mass from the same species showed negligible differences (OLS regression: P < 0.001, ECV = 0.995[mass] + 0.011) with the slope not significantly different to one (P = 0.490) and the intercept not significantly different to 0 (P = 0.568)”

• AssumptionThe authors state this as an assumption: A 1 g/cc^3 relationship between brain volume and brain mass holds for species for which only volumetric data are available.

May combine two claims.

Cetaceans reached high levels of encephalization long before primates, and primates only exceeded cetaceans with the emergence of Homo.

“It is clear from this that cetaceans reached high levels of encephalization long before primates, and primates only exceeded cetaceans with the emergence of Homo (Fig. 5).”

May combine two claims.

Mysticete brain and body mass evolved with directional trends to increase, but EQ did not.

“our ancestral state reconstructions suggest that mysticete brain and body mass evolved with directional trends to increase; but EQ did not.”

May combine two claims.

Results are stable to the inclusion or exclusion of different extinct taxa and suggest the approach taken is robust.

“The results are stable to the inclusion/exclusion of different extinct taxa and suggest the approach taken is robust (Supporting Information).”

May combine two claims.

The data set includes 13 of 14 extant families (93%) and fossil taxa span a range of key taxonomic transitions.

“In this regard our data set includes 13 of 14 extant families (93%) and our fossil taxa span a range of key taxonomic transitions.”

Classified as probably not a substantial claim. May combine two claims.

Brain and body mass evolution has become developmentally decoupled in primates, and selection may have acted on the developmental mechanisms controlling brain mass.

“This suggests that brain and body mass evolution has become developmentally decoupled in primates (Lande 1979) and that selection may have acted on the developmental mechanisms controlling brain mass (Montgomery et al. 2011;Montgomery and Mundy 2012).”

• cites Lande 1979 sourceNot checked — no full text of the source
• cites Montgomery et al. 2011 sourceNot checked — no full text of the source
• cites Montgomery and Mundy 2012 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

The G. macrorhynchus body mass estimate lies toward the lower end of the adult range and may be a subadult, which could inflate EQ.

“but note the G. macrorhynchus body mass estimate lies toward the lower end of the adult range and may be a subadult which could inflate EQ”

May combine two claims.

The data set includes 42 extant species, about 48% of living species, and 20 extinct species, about 4% of valid extinct species.

“In total, our data set includes 42 extant species, ∼48% of living species, and 20 extinct species, ∼4% of valid extinct species (Supporting Information).”

Classified as probably not a substantial claim. May combine two claims.

MCMC settings were sufficient to achieve chain convergence with acceptable range of data deviation values for all nodes except the basal node, which was run longer.

“These settings were sufficient to achieve chain convergence with acceptable range of data deviation values for all nodes except the basal node for which the MCMC chain was run for 7.5 million generations with a burn-in of 3 million generations.”

Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

It has been argued that aquatic weightlessness will lead to underestimates of encephalization for many cetaceans when compared to terrestrial mammals.

“It has been argued that this will lead to underestimates of encephalization for many cetaceans when compared to terrestrial mammals (Harvey and Krebs 1990).”

• cites Harvey and Krebs 1990 sourceNot checked — no full text of the source

May combine two claims.

The few Oligocene odontocetes whose inner ears have been studied in detail resemble the ears of extant odontocetes, suggesting they were specialized for hearing high-frequency sounds.

“The few Oligocene odontocetes whose inner ears have been studied in detail resemble the ears of extant odontocetes (Fleischer 1976;Luo and Eastman 1995), suggesting they were specialized for hearing high-frequency sounds.”

• cites Fleischer 1976Not checked — no full text of the source
• cites Luo and Eastman 1995 sourceNot checked — no full text of the source

May combine two claims.

Mysticetes appear to have divergent developmental trajectories compared to odontocetes, with extremely high rates of both pre-and postnatal body growth.

“Although data are limited, mysticetes do appear to have divergent developmental trajectories compared to odontocetes, with extremely high rates of both pre-and postnatal body growth (Frazer and Hugget 1973).”

• cites Frazer and Hugget 1973 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

Lande (1979) postulated that the genetic basis of brain and body mass evolution in primates may have become increasingly decoupled to facilitate an evolutionary expansion of the brain without leading to gigantism and antagonistic selection on body mass.

“For example, Lande (1979) postulated that the genetic basis of brain and body mass evolution in primates may have become increasingly decoupled to facilitate an evolutionary expansion of the brain without leading to gigantism and antagonistic selection on body mass.”

• cites Lande 1979 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S4 (based).

Lineage-specific selection pressures presumably resulted in some cetaceans becoming highly encephalized.

“Although EQ has not evolved by a directional, increasing trend in cetaceans, lineage-specific selection pressures presumably resulted in some cetaceans becoming highly encephalized.”

Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

The stasis in brain size during the period immediately subsequent to the origin of Odontoceti may reflect stabilizing selection on brain mass whereas directional selection acted to decrease body mass.

“it may be that the stasis in brain size during this period reflects stabilizing selection on brain mass whereas direc-tional selection acted to decrease body mass.”

May combine two claims.

Von Economo neurons are found in both mysticetes and odontocetes and, as in hominoid primates, show a derived regionally specific distribution.

“Von Economo neurons, which may be linked to some higher cognitive faculties (Allman et al. 2005;Butti et al. 2013), are found in both mysticetes and odontocetes (Butti et al. 2009) and, as in hominoid primates, show a derived regionally specific distribution (Butti and Hoff 2010;Butti et al. 2011).”

• cites Butti et al. 2009 sourceNot checked — no full text of the source
• cites Butti and Hoff 2010Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Butti et al. 2011 sourceNot checked — no full text of the source

May combine two claims.

Shifts in such constraints in marine habitats likely result in a rebalancing of this trade-off and may contribute to the altered brain:body allometry seen in cetaceans.

“Shifts in such constraints in marine habitats likely results in a rebalancing of this trade-off and may contribute to the altered brain:body allometry seen in cetaceans.”

May combine two claims.

Limited data on neuron numbers suggest that, despite large size differences, mysticete and odontocete brains have similar numbers of neurons, both being comparable to the number found in an average chimpanzee brain.

“Limited data on neuron numbers suggest that, despite large size differences, mysticete and odontocete brains have similar numbers of neurons (Oelschläger and Oelschläger 2002;Eriksen and Pakkenberg 2007), both being comparable to the number found in an average chimpanzee brain (Huggenberger 2008).”

• cites Oelschläger and Oelschläger 2002Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Eriksen and Pakkenberg 2007 sourceNot checked — no full text of the source
• cites Huggenberger 2008 sourceNot checked — no full text of the source

May combine two claims.

The low EQs of mysticetes have previously been attributed to differences in blubber content, which may deflate EQ in large whales, but this appears to have a minimal effect.

“Although the low EQs of mysticetes have previously been attributed to differences in blubber content, which may deflate EQ in large whales, this appears to have a minimal effect (Tartarelli and Bisconti 2006).”

• cites Tartarelli and Bisconti 2006 sourceNot checked — no full text of the source

May combine two claims.

A recent simulation study suggests that the inclusion of even a small proportion of extinct diversity can improve our ability to select the best-fitting model of evolution and obtain improved reconstruction of a trait's evolutionary history.

“a recent simulation study suggests that the inclusion of even a small proportion of extinct diversity can improve our ability to select the best-fitting model of evolution and obtain improved reconstruction of a trait's evolutionary history (Slater et al. 2012).”

• cites Slater et al. 2012 sourceNot checked — no full text of the source

May combine two claims.

These behaviors are observed in some odontocetes and primates, and are considered cognitively demanding.

“These behaviors are observed in some odontocetes and primates, and are considered cognitively demanding (Barrett et al. 2003;Simmonds 2006).”

• cites Barrett et al. 2003 sourceNot checked — no full text of the source
• cites Simmonds 2006 sourceNot checked — no full text of the source

May combine two claims.

Cetaceans have pursued an alternative route to complexity by multiplying existing structures, resulting in a thin but highly folded cortex.

“cetaceans have pursued an alternative route to complexity by multiplying existing structures (Morgane et al. 1990;Marino 2004;Huggenberger 2008) resulting in a thin but highly folded cortex (Morgane et al. 1990;Marino 2004b;Huggenberger 2008).”

• cites Morgane et al. 1990 sourceNot checked — no full text of the source
• cites Marino 2004Not matched

  Couldn’t be matched to a paper in Crossref, so it can’t be checked.

• cites Huggenberger 2008 sourceNot checked — no full text of the source

Probably not a substantial claim: may not pass S4 (based).

This type of elaboration may have not been available to smaller-bodied terrestrial mammals due to mechanical and gravitational constraints favoring more size-efficient schemes of cortical elaboration.

“This type of elaboration may have not been available to smaller-bodied terrestrial mammals due to mechanical and gravitational constraints favoring more size-efficient schemes of cortical elaboration.”