Establishing an independent academic identity is a central yet insufficiently understood challenge for early-career researchers. However, limited resources and mentor-driven research agendas often constrain early efforts toward autonomy. To provide large-scale quantitative evidence on how junior researchers develop independence, we introduce a framework that traces how mentees diverge from their mentors in both research topics and collaboration networks, and how these divergences relate to long-term scientific impact. Analyzing over 500,000 mentee-mentor pairs in Chemistry, Neuroscience, and Physics across six decades, we find that high-impact scientists often initiate work in secondary areas of their mentors' expertise while adaptively establishing distinct research trajectories. This pattern is most pronounced among mentees who eventually surpass their mentors' impact. We identify an inverted U-shaped relationship between topic divergence and mentees' enduring impact, with moderate divergence yielding the highest scientific impact, revealing an independence paradox in scientific careers. This pattern holds whether topic divergence is measured by citation network or semantic thematic distance. We further reveal that excessive direct mentor-mentee collaborations correlate with lower mentee impact, whereas expanding professional networks to include mentors' collaborators is beneficial. These findings not only offer actionable guidance for early-career researchers navigating independence but also inform institutional policies that promote mentorship structures supporting intellectual innovation and recognizing original contributions in promotion evaluations.

翻译：建立独立的学术身份是早期职业研究人员面临的核心挑战，但人们对此理解尚不充分。然而，资源有限与以导师为主导的研究议程常常制约着早期自主性的探索。为系统量化初级研究人员如何培养独立性的证据，我们提出一个分析框架，追踪学员在研究主题与合作网络两方面与导师的分化轨迹，并探究这些分化与长期科学影响力的关联。通过对化学、神经科学和物理学三个领域六十年间超过50万组学员-导师配对数据的分析，我们发现：高影响力科学家往往从导师专长领域的次级方向起步，同时灵活构建差异化的研究路径。这一特征在最终超越导师影响力的学员群体中尤为显著。我们揭示了主题分化与学员持久影响力之间的倒U型关系——适度分化能产生最高科学影响力，由此呈现科学职业中的独立性悖论。无论以引文网络还是语义主题距离衡量主题分化程度，该规律均成立。研究进一步表明：过多的直接导师-学员合作与较低学员影响力相关，而拓展包含导师合作者的专业网络则具有积极效应。这些发现不仅为早期研究人员寻求独立性提供可操作指导，亦为制定促进学术创新的导师制度、在晋升评审中认可原创贡献的机构政策提供依据。