1. Systems Engineering Institute, Xi’an Jiaotong University, Xi’an, Shaanxi 710049, P.R. China
2. Department of Biostatistics, University of Michigan, Ann Arbor, MI 48109, USA
3. Center for Statistical Genetics, University of Michigan, Ann Arbor, MI 48109, USA
4. Departments of Statistical Science, Mathematics, and Computer Science, Duke University, Durham, NC 27708, USA
5. Departments of Evolutionary Anthropology and Biology, Duke University, Durham, NC 27708, USA
6. Duke University Population Research Institute, Duke University, Durham, NC 27708, USA