如果你想要快速回顧一下人類大腦在過去2500萬年內(nèi)的進(jìn)化史，只需要觀察嬰兒到成人大腦的成長歷程就可以了,。在人最初的幾十年內(nèi),，大腦最外層的多褶皺部分——大腦皮層——正重演著人類從猿類中分化出來并進(jìn)一步演化的歷程。
（圖片來源：PNAS)
“這并不是說某種一對(duì)一的精確對(duì)應(yīng),，但是雙方相似的部分實(shí)在引人注目,，讓人無法忽略，”來自華盛頓大學(xué)圣路易斯分校的神經(jīng)生物學(xué)家大衛(wèi)·馮·埃森(David Van Essen)說,。在7月12日出版的美國《國家科學(xué)院院刊》（PNAS）上,，馮·埃森領(lǐng)導(dǎo)的小組比較了人類嬰兒和成年人的大腦掃描結(jié)果。結(jié)果顯示的差異性被用來和另一掃描結(jié)果進(jìn)行對(duì)比,，即成年人類和短尾猴的大腦皮層形狀差異,。在大約2500萬年前，人類和短尾猴擁有共同的祖先,。
自那以后,，人類大腦經(jīng)歷了超速發(fā)展，變得異常巨大而復(fù)雜,。雖然并非所有變化都牽涉到大小和形狀,，人類同時(shí)也發(fā)展出了嶄新的基因系統(tǒng)，并且以完全不同的方式運(yùn)行,，但所有這些變化都毫無疑問屬于人類進(jìn)化歷程的一部分。而在嬰兒時(shí)期,，人類大腦尚未發(fā)育完全,，因而顯得非常幼小。根據(jù)馮·埃森的說法,，這種大腦發(fā)展模式可能代表了由于不斷進(jìn)化而產(chǎn)生的一種優(yōu)勢(shì)策略,。
此項(xiàng)最新研究發(fā)現(xiàn)，不論是嬰兒和成年人之間還是人類和猿猴之間,，大腦在成長中變化最小的是那些和最重要的核心感覺相關(guān)的部位,，如視覺。很顯然,，這些感覺是從出生起就非常重要的,。而如果其他一些不那么重要的大腦部分也同樣發(fā)育成熟的話，嬰兒的腦袋就將顯得很大,，而這顯然會(huì)對(duì)懷孕期間造成麻煩,。
“這一先后的發(fā)育順序同時(shí)還使大腦的晚發(fā)育部分有機(jī)會(huì)得到童年時(shí)代的經(jīng)驗(yàn)學(xué)習(xí)”，馮·埃森說,。巨量的社會(huì)文化經(jīng)驗(yàn)充實(shí)了嬰兒的大腦,，使嬰兒以及整個(gè)人類種族具有更強(qiáng)的適應(yīng)能力,，也使發(fā)展復(fù)雜的社會(huì)體制成為可能。“相對(duì)其他靈長類動(dòng)物而言,，人類的童年期相對(duì)較長”,，馮·埃森說。“我們學(xué)習(xí)大量的知識(shí)技能,，但這也要花費(fèi)大量的時(shí)間,。”(生物谷Bioon.net)
生物谷推薦原文出處：
PNAS doi: 10.1073/pnas.1001229107
Similar patterns of cortical expansion during human development and evolution
Jason Hilla,1, Terrie Indera, Jeffrey Neila, Donna Dierkerb, John Harwellb, and David Van Essenb
Departments of a Pediatrics and b Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, MO 63108
The cerebral cortex of the human infant at term is complexly folded in a similar fashion to adult cortex but has only one third the total surface area. By comparing 12 healthy infants born at term with 12 healthy young adults, we demonstrate that postnatal cortical expansion is strikingly nonuniform: regions of lateral temporal, parietal, and frontal cortex expand nearly twice as much as other regions in the insular and medial occipital cortex. This differential postnatal expansion may reflect regional differences in the maturity of dendritic and synaptic architecture at birth and/or in the complexity of dendritic and synaptic architecture in adults. This expression may also be associated with differential sensitivity of cortical circuits to childhood experience and insults. By comparing human and macaque monkey cerebral cortex, we infer that the pattern of human evolutionary expansion is remarkably similar to the pattern of human postnatal expansion. To account for this correspondence, we hypothesize that it is beneficial for regions of recent evolutionary expansion to remain less mature at birth, perhaps to increase the influence of postnatal experience on the development of these regions or to focus prenatal resources on regions most important for early survival.
