defining feature 这里的defining是什么意思 怎么翻译

I propose a
conceptual extension of the theory of cultural evolution, particularly related to the
evolutionary competition between cultural groups. The key concept in this extension is
the emergent group-level trait. This type of trait is characterized by the structured
organization of differentiated individuals, and constitutes a unit of selection that is
qualitatively different from selection on groups as defined by traditional multilevel
selection (MLS) theory. As a corollary, I argue that the traditional focus on cooperation
as the defining feature of human societies has missed an essential feature of cooperative
groups.

特异性特征 定义性特征（defining feature）是定义一个概 念的必要且充分的特征。

define 是定义，给。。。下定义，为。。。界定概念的意思。
as the defining featureof human societies是说： 我认为，传统意义上将合作看作是人类社会的一个定义性特征（就是人类社会的特性之一就是合作），这一观点并未考虑到合作性群体这一必要特征。

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