Does the Buddha deny genetic differences?
MN 98 is about "jati" or "social identity". The Buddha says physical birth or "ancestry" is unrelated to jati; that the jatis are verbal designations assigned due to kamma (actions). 

For example, Michael Jordan's great great grandparents were probably slaves. Where as Michael Jordan was a sporting superstar &amp; billionaire. Jordan was born at Cumberland Hospital in Fort Greene, Brooklyn, to Deloris, who worked in banking, and James R. Jordan Sr., an equipment supervisor. These distinctions of "slave", "banker", "supervisor" vs "basketball billionaire" are not related to physical birth or ancestry. They are related to social kamma (activity). 

Albert Einstein was a German-born theoretical physicist. His parents were Hermann Einstein, a salesman and engineer, and Pauline Koch. The Einsteins were non-observant Ashkenazi Jews, and Albert attended a Catholic elementary school.


  You’re a brahmin by your deeds, Kammunā brāhmaṇo hoti,
  
  and by deeds a non-brahmin. kammunā hoti abrāhmaṇo.
  
  You’re a farmer by your deeds, Kassako kammunā hoti,
  
  by deeds you’re a professional; sippiko hoti kammunā;
  
  you’re a trader by your deeds, Vāṇijo kammunā hoti,
  
  by deeds are you an employee; pessako hoti kammunā.
  
  you’re a bandit by your deeds, Coropi kammunā hoti,
  
  by deeds you’re a soldier; yodhājīvopi kammunā;
  
  you’re a sacrificer by your deeds, Yājako kammunā hoti,
  
  by deeds you’re a ruler. rājāpi hoti kammunā.
  
  In this way in accord with truth, Evametaṃ yathābhūtaṃ,
  
  the astute regard deeds. kammaṃ passanti paṇḍitā;
  
  Seeing dependent origination, Paṭiccasamuppādadassā,
  
  they’re expert in deeds and their results. kammavipākakovidā.
  
  Deeds make the world go on, Kammunā vattati loko,
  
  deeds make people go on; kammunā vattati pajā;
  
  sentient beings are bound by deeds, Kammanibandhanā sattā,
  
  like a moving chariot’s linchpin. rathassāṇīva yāyato.
  
  MN 98