  Leadership is evolving dynamically from an individual endeavor to shared
efforts. This paper aims to advance our understanding of shared leadership in
scientific teams. We define three kinds of leaders, junior (10-15), mid
(15-20), and senior (20+) based on career age. By considering the combinations
of any two leaders, we distinguish shared leadership as heterogeneous when
leaders are in different age cohorts and homogeneous when leaders are in the
same age cohort. Drawing on 1,845,351 CS, 254,039 Sociology, and 193,338
Business teams with two leaders in the OpenAlex dataset, we identify that
heterogeneous shared leadership brings higher citation impact for teams than
homogeneous shared leadership. Specifically, when junior leaders are paired
with senior leaders, it significantly increases team citation ranking by 1-2%,
in comparison with two leaders of similar age. We explore the patterns between
homogeneous leaders and heterogeneous leaders from team scale, expertise
composition, and knowledge recency perspectives. Compared with homogeneous
leaders, heterogeneous leaders are more adaptive in large teams, have more
diverse expertise, and trace both the newest and oldest references.
