The emergence of a coordinated network of cognitive and speech genes in the human lineage performing overlapping functions is a great evolutionary puzzle. Prior studies on the speech gene FOXP2 are inconclusive on the nature of selection operating on this gene in the human lineage. Here, I show that the evolution of FOXP2 is accelerated in the human lineage due to relaxation of purifying selection (relaxed selection). Five potential genes associated with human-specific intelligence and speech genes have evolved under the impact of positive selection and three genes including FOXP2 have undergone relaxation of purifying selection in the human lineage. Overall, three evolutionary processes namely positive selection, relaxation of purifying selection and neutral evolution have contributed for the genomic evolution of extraordinary cognitive ability and speech in the hominin lineage. The cognitive and speech genes subjected to natural selection in the human lineage have demonstrated a coevolutionary trend.

中文翻译：

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认知和语言基因是由人类谱系中的积极选择和放松选择共同塑造的。

在执行重叠功能的人类谱系中，认知和语音基因的协调网络的出现是一个巨大的进化难题。先前对语音基因 FOXP2 的研究对于人类世系中对该基因进行选择的性质尚无定论。在这里，我展示了 FOXP2 的进化在人类谱系中由于净化选择（放松选择）的放松而加速。在正选择的影响下，与人类特定的智力和语言基因相关的五个潜在基因已经进化，包括 FOXP2 在内的三个基因在人类谱系中经历了净化选择的放松。总体而言，三个进化过程即正选择、净化选择和中性进化的放松有助于人类谱系中非凡认知能力和语言的基因组进化。人类谱系中经历自然选择的认知和语音基因已表现出协同进化的趋势。