中時在9月3日引述中央社新聞刊登了以下的報導, 文中說到"老虎的腦容量高於獅子因此老虎較聰明"這樣的觀點. 然而無論是Yamaguchi等人的原始論文, 或牛津大學的新聞稿, 都沒有提到所謂的腦大=智慧高這樣的論述. 事實上Yamaguchi等人的論文所談到的預測(prediction)是社會性動物腦容量相對身體體積的比例應較獨居性動物為高, 然而他們的度量分析卻得到相反的結果. 這個預測的來源是根據"社會性動物的腦部可能要處理更複雜的資訊因此腦部容量可能較高"的預設(assumption). 因此中央社的編譯直接把這篇文章的結果直接詮釋為老虎的智慧較高犯了"引用失當"及"過度解讀"的毛病, 更不要瞎扯"演化論"了. 牛津大學新聞稿的原文使用"brainier"這個字的原意其實是"比較有腦"或"比較精明", 這個brainier相對於brainless, 也就是我們所說的"無腦"或近似"腦殘"(retarded)之意, 平常用來暗指一個人的邏輯有沒有問題, 也就是說牛津的新聞稿事實上也只是使用brain vs brainier這兩個字對閱聽人的吸引力來闡述這項研究成果, 但是這篇論文本身絕對沒有比較虎獅智慧的意圖. 有關brain size與intelligence之間的關聯有非常多的文章討論, 影響intelligence的因素何其多? 若brain size如此單純地同等於智能的高低, 那麼我們又如何解釋為何現代智人的腦容量較尼安德塔人小呢?
以下是中國時報引用中央社的新聞:
牛津大學研究：老虎智商高於獅子 2009-09-03
新聞速報 中央社
獅子被稱為萬獸之王，但根據英國牛津大學動物學家的研究，獅子的智商卻低於老虎。
牛津大學研究人員從全世界博物館，對370頭獅子、225頭老虎、32頭美洲豹及42頭豹的頭蓋骨及腦容量進行研究，雖然老虎與獅子的身型相似，但老虎的腦容量較獅子大約16%。
就進化論而言，腦的大小與智商相關，腦部愈大，智商也愈高。
進行這項研究的牛津大學野生動物保育研究小組山口教授（Nobby Yamaguchi）指出，令人意外的是，在屬同一科的四種動物研究，老虎的腦部相對最大。
他說，雖然獅子的頭蓋骨平均來看大於老虎，但是老虎的腦容量大於獅子，「令人驚訝的是，身型嬌小的巴里（Balinese）雌虎腦容量，和南非公獅一般大」。
山口教授指出，雖然腦容量小於老虎，但獅子仍是食物鏈的最上端，「好群居的獅子可以攻擊愛獨居的老虎，但是也許老虎夠聰明，可以躲開獅子的攻擊」。
下一步研究人員將研究，老虎腦部的那一個部分大於獅子，並進一步了解，為何老虎需要較大的腦。980903
獅子被稱為萬獸之王，但根據英國牛津大學動物學家的研究，獅子的智商卻低於老虎。
牛津大學研究人員從全世界博物館，對370頭獅子、225頭老虎、32頭美洲豹及42頭豹的頭蓋骨及腦容量進行研究，雖然老虎與獅子的身型相似，但老虎的腦容量較獅子大約16%。
就進化論而言，腦的大小與智商相關，腦部愈大，智商也愈高。
進行這項研究的牛津大學野生動物保育研究小組山口教授（Nobby Yamaguchi）指出，令人意外的是，在屬同一科的四種動物研究，老虎的腦部相對最大。
他說，雖然獅子的頭蓋骨平均來看大於老虎，但是老虎的腦容量大於獅子，「令人驚訝的是，身型嬌小的巴里（Balinese）雌虎腦容量，和南非公獅一般大」。
山口教授指出，雖然腦容量小於老虎，但獅子仍是食物鏈的最上端，「好群居的獅子可以攻擊愛獨居的老虎，但是也許老虎夠聰明，可以躲開獅子的攻擊」。
下一步研究人員將研究，老虎腦部的那一個部分大於獅子，並進一步了解，為何老虎需要較大的腦。980903
我們再看牛津大學所發出的新聞稿
Are tigers ‘brainier’ than lions?
Science
03 Sep 09
The Siberian tiger - found to be the 'closest molecular neighbour' to the extinct Caspian tiger
Tigers have bigger brains relative to their body size than lions. Photo credit: Raffinger Enikö
A wide-ranging study of big cat skulls, led by Oxford University scientists, has shown that tigers have bigger brains, relative to their body size, than lions, leopards or jaguars.
The team investigated the relationship between the skull size – the longest length between the front and back parts of the skull – of a large sample of tigers, lions, leopards and jaguars and the volume inside the cats’ respective craniums. The researchers report their findings in this month’s Biological Journal of the Linnean Society.
'What we had not expected is that the tiger has clearly much bigger relative brain size than do the other three species, which all have similar relative brain sizes,’ said Dr Nobby Yamaguchi of Oxford University’s Wildlife Conservation Research Unit (WildCRU), an author of the report with WildCRU Director Professor David Macdonald.
‘When we compare the two biggest species, on average the lion has a bigger skull than the tiger based on the greatest length of the skull. However, the tiger has bigger cranial volume than the lion. It is truly amazing that tiny female Balinese tiger skulls have cranial volumes as large as those of huge male southern African lion skulls.’
What we had not expected is that the tiger has clearly much bigger relative brain size than do the other three species, which all have similar relative brain sizes.
Dr Nobby Yamaguchi
It has sometimes been assumed that social species, such as lions, should have larger brains than solitary species, such as tigers, because of the need to handle a more complex social life within groups or prides. However, despite a few studies suggesting a relationship between big brains and sociality in mammals, evidence for the link is far from clear.
Dr Nobby Yamaguchi said: ‘Our results strongly suggest that there is no detectable positive relationship between relative brain size and sociality amongst these four big cat species, which shared a common ancestor around 3.7 million years ago.’
The team also looked at the popular idea that tigers are ‘bigger’ than lions (which could mean that the tiger’s relatively bigger brain size simply reflects its bigger body). However, careful re-evaluation of original field data and relatively well-documented hunting records does not support this idea.
So the team concluded that the tigers have a relatively bigger brain (around 16 per cent larger) than lions, given their very similar average body sizes.
Professor Macdonald said: ‘Two general lessons emerge from our findings: first, how much remains to be discovered about even these most familiar of big cats, and second how important museum collections can be as a source of unexpected insights.’
The next step for the researchers is to try to answer whether such a difference can be explained by intrageneric variation or merely by chance. If not by chance, then it raises the question why the tiger evolved a relatively bigger brain (or why other species evolved smaller brains) after the tiger’s ancestor split from the common ancestor to the other three species.
The answers to both these questions may lie in analysing comparative brain anatomy amongst these species (for instance, which parts of the tiger’s brain are bigger than the lion’s) and similar data from extinct relatives of these big cats as well as smaller living relatives such as the snow leopard and clouded leopard.
Science
03 Sep 09
The Siberian tiger - found to be the 'closest molecular neighbour' to the extinct Caspian tiger
Tigers have bigger brains relative to their body size than lions. Photo credit: Raffinger Enikö
A wide-ranging study of big cat skulls, led by Oxford University scientists, has shown that tigers have bigger brains, relative to their body size, than lions, leopards or jaguars.
The team investigated the relationship between the skull size – the longest length between the front and back parts of the skull – of a large sample of tigers, lions, leopards and jaguars and the volume inside the cats’ respective craniums. The researchers report their findings in this month’s Biological Journal of the Linnean Society.
'What we had not expected is that the tiger has clearly much bigger relative brain size than do the other three species, which all have similar relative brain sizes,’ said Dr Nobby Yamaguchi of Oxford University’s Wildlife Conservation Research Unit (WildCRU), an author of the report with WildCRU Director Professor David Macdonald.
‘When we compare the two biggest species, on average the lion has a bigger skull than the tiger based on the greatest length of the skull. However, the tiger has bigger cranial volume than the lion. It is truly amazing that tiny female Balinese tiger skulls have cranial volumes as large as those of huge male southern African lion skulls.’
What we had not expected is that the tiger has clearly much bigger relative brain size than do the other three species, which all have similar relative brain sizes.
Dr Nobby Yamaguchi
It has sometimes been assumed that social species, such as lions, should have larger brains than solitary species, such as tigers, because of the need to handle a more complex social life within groups or prides. However, despite a few studies suggesting a relationship between big brains and sociality in mammals, evidence for the link is far from clear.
Dr Nobby Yamaguchi said: ‘Our results strongly suggest that there is no detectable positive relationship between relative brain size and sociality amongst these four big cat species, which shared a common ancestor around 3.7 million years ago.’
The team also looked at the popular idea that tigers are ‘bigger’ than lions (which could mean that the tiger’s relatively bigger brain size simply reflects its bigger body). However, careful re-evaluation of original field data and relatively well-documented hunting records does not support this idea.
So the team concluded that the tigers have a relatively bigger brain (around 16 per cent larger) than lions, given their very similar average body sizes.
Professor Macdonald said: ‘Two general lessons emerge from our findings: first, how much remains to be discovered about even these most familiar of big cats, and second how important museum collections can be as a source of unexpected insights.’
The next step for the researchers is to try to answer whether such a difference can be explained by intrageneric variation or merely by chance. If not by chance, then it raises the question why the tiger evolved a relatively bigger brain (or why other species evolved smaller brains) after the tiger’s ancestor split from the common ancestor to the other three species.
The answers to both these questions may lie in analysing comparative brain anatomy amongst these species (for instance, which parts of the tiger’s brain are bigger than the lion’s) and similar data from extinct relatives of these big cats as well as smaller living relatives such as the snow leopard and clouded leopard.
以下為Yamaguchi et al. (2009)發表於Biological Journal of the Linnean Society 98(1): 95-93論文的摘要:
Intraspecific encephalization of the lion and the tiger is investigated for the first time using a very large sample. Using cranial volume as a measure of brain size, the tiger has a larger brain relative to greatest length of skull than the lion, the leopard and the jaguar. The Asian lion has a relatively much smaller brain compared with those of sub-Saharan lions, between which there are few differences. The Balinese and Javan tigers had relatively larger brains compared with those of Malayan and Sumatran tigers, even although these four putative subspecies occupy adjacent ranges in south-eastern Asia. Differences in brain size do not appear to correlate with any known differences in behaviour and ecology and, therefore, may reflect only chance differences in intrageneric and intraspecific phylogeny. However, captive-bred big cats generally have a reduced brain size compared with that of wild animals, so that an animal's life history and living conditions may affect brain size and, hence, functional or environmental explanations should be considered when linking brain size differences to intraspecific phylogenies.
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