The evolution of the modern human brain was accompanied by distinct molecular and cellular specializations, which underpin our diverse cognitive abilities but also increase our susceptibility to neurological diseases. These features, some specific to humans and others shared with related species, manifest during different stages of brain development. In this multi-stage process, neural stem cells proliferate to produce a large and diverse progenitor pool, giving rise to excitatory or inhibitory neurons that integrate into circuits during further maturation. This process unfolds over varying time scales across species and has progressively become slower in the human lineage, with differences in tempo correlating with differences in brain size, cell number and diversity, and connectivity. Here we introduce the terms ‘bradychrony’ and ‘tachycrony’ to describe slowed and accelerated developmental tempos, respectively. We review how recent technical advances across disciplines, including advanced engineering of in vitro models, functional comparative genetics and high-throughput single-cell profiling, are leading to a deeper understanding of how specializations of the human brain arise during bradychronic neurodevelopment. Emerging insights point to a central role for genetics, gene-regulatory networks, cellular innovations and developmental tempo, which together contribute to the establishment of human specializations during various stages of neurodevelopment and at different points in evolution.

现代人类大脑的进化伴随着独特的分子和细胞专业化，这支撑了我们多样化的认知能力，但也增加了我们对神经系统疾病的易感性。这些特征，有些是人类特有的，有些是相关物种共有的，在大脑发育的不同阶段表现出来。在这个多阶段过程中，神经干细胞增殖产生大量且多样化的祖细胞库，产生兴奋性或抑制性神经元，并在进一步成熟过程中整合到回路中。这一过程在不同物种中以不同的时间尺度展开，并且在人类谱系中逐渐变慢，节奏的差异与大脑大小、细胞数量和多样性以及连接性的差异相关。在这里，我们引入术语“bradychrony”和“tachychrony”来分别描述减缓和加速的发育节奏。我们回顾了跨学科的最新技术进步，包括体外模型的先进工程、功能比较遗传学和高通量单细胞分析，如何导致人们更深入地了解人类大脑在慢性神经发育过程中如何产生专业化。新的见解指出遗传学、基因调控网络、细胞创新和发育节奏的核心作用，它们共同有助于在神经发育的不同阶段和进化的不同阶段建立人类专业化。