Historical clue formulations

• What "F" can stand for — 2025-09-09
• Like does — 2025-05-01
• "F," on a form — 2020-09-17
• Like about half of all deliveries? — 2016-02-07
• Like dams — 2015-09-13
• One with XX chromosomes — 2015-05-11
• XX — 2013-03-30
• Like fillies but not billies — 2004-04-20
• Egg producer — 1999-11-17
• Kipling's "The ___ of the Species" — 1998-07-02
• Hen or pen, e.g. — 1997-05-03
• Pistil-packing — 1997-01-18
• Having two X chromosomes — 1995-02-15