新的研究結(jié)果顯示，在印度尼西亞發(fā)現(xiàn)的近似人類化石,，應(yīng)該就是人類的一支,。自從6年前發(fā)現(xiàn)了這個(gè)以電影《指環(huán)王》內(nèi)容中的小矮人而被昵稱為“霍比特人”的化石之后，學(xué)界便一直為如何將之分類而爭辯不休,。
“霍比特人”的身高只有大約4英尺,，腦部大小和黑猩猩差不多。據(jù)認(rèn)為,，“霍比特人”是從大約一百萬年前抵達(dá)印尼弗羅里斯島的人類遠(yuǎn)祖演化而成的侏儒,。
但是不贊同此一理論的人士則說，“霍比特人”的腦部太小,，而一個(gè)正常大小的人類的腦部不可能會(huì)因?yàn)檠莼s小到這種地步,。
但是在《自然期刊》上發(fā)表的研究報(bào)告說說，在研究了侏儒河馬的頭骨之后,，證明同類動(dòng)物的頭骨在演化過程當(dāng)中的確可以縮小很多,。
參與研究的英國自然科學(xué)博物館的溫登博士說， “霍比特人”一直讓科學(xué)家們想不透,，因?yàn)?ldquo;霍比特人”的腦部只有黑猩猩一樣的大小,。這是在其他遠(yuǎn)古人類研究上從來沒見到過的現(xiàn)象。
溫登博士認(rèn)為,，如果以距離現(xiàn)代人類較近的直立猿人的身子和腦部的比例來計(jì)算的話,，“霍比特人”腦部比較小,，其實(shí)也不是不合道理的。
另外一個(gè)針對(duì)“霍比特人”足部所作的研究,，則是把結(jié)果發(fā)表在《人類進(jìn)化期刊》上,。這個(gè)研究認(rèn)為，“霍比特人”是從東南亞本地的遠(yuǎn)古人類進(jìn)化而來的,。
這兩個(gè)研究的結(jié)果,，雖然不一定證明了“霍比特人”絕對(duì)是人類的遠(yuǎn)祖的一支，但是卻證明了人類的進(jìn)化史要比以前想象的更加復(fù)雜,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 459, 85-88 (7 May 2009) | doi:10.1038/nature07922
Insular dwarfism in hippos and a model for brain size reduction in Homo floresiensis
Eleanor M. Weston1 & Adrian M. Lister1
1 Department of Palaeontology, Natural History Museum, London SW7 5BD, UK
Body size reduction in mammals is usually associated with only moderate brain size reduction, because the brain and sensory organs complete their growth before the rest of the body during ontogeny1, 2. On this basis, 'phyletic dwarfs' are predicted to have a greater relative brain size than 'phyletic giants'1, 3. However, this trend has been questioned in the special case of dwarfism of mammals on islands4. Here we show that the endocranial capacities of extinct dwarf species of hippopotamus from Madagascar are up to 30% smaller than those of a mainland African ancestor scaled to equivalent body mass. These results show that brain size reduction is much greater than predicted from an intraspecific 'late ontogenetic' model of dwarfism in which brain size scales to body size with an exponent of 0.35. The nature of the proportional change or grade shift2, 5 observed here indicates that selective pressures on brain size are potentially independent of those on body size. This study demonstrates empirically that it is mechanistically possible for dwarf mammals on islands to evolve significantly smaller brains than would be predicted from a model of dwarfing based on the intraspecific scaling of the mainland ancestor. Our findings challenge current understanding of brain–body allometric relationships in mammals and suggest that the process of dwarfism could in principle explain small brain size, a factor relevant to the interpretation of the small-brained hominin found on the Island of Flores, Indonesia6.
