8.31 avg 10 episodes 8.1 → 8.9 45 min avg
| # | Title | Rating | Votes |
|---|---|---|---|
| 1 | Natural Selection | 8.1 | 3,045 |
| 2 | Instinct | 8.0 | 2,492 |
| 3 | Variation Under Nature | 8.1 | 2,330 |
| 4 | Effects of External Conditions | 8.2 | 2,206 |
| 5 | Conditions of Existence | 8.2 | 2,143 |
| 6 | Variations Under Domestication | 8.4 | 2,191 |
| 7 | Parts Developed in an Unusual Manner | 8.1 | 2,065 |
| 8 | Entangled Bank | 8.5 | 2,074 |
| 9 | Unconscious Selection | 8.6 | 2,064 |
| 10 | Endless Forms Most Beautiful | 8.9 | 2,316 |
8.32 avg 10 episodes 8.4 → 9.0 44 min avg
| # | Title | Rating | Votes |
|---|---|---|---|
| 1 | Nature Under Constraint and Vexed | 8.4 | 1,995 |
| 2 | Governed by Sound Reason and True Religion | 8.2 | 1,774 |
| 3 | Mingling Its Own Nature with It | 8.0 | 1,711 |
| 4 | Governed as It Were by Chance | 8.4 | 1,738 |
| 5 | Ipsa Scientia Potestas Est | 8.2 | 1,660 |
| 6 | To Hound Nature in Her Wanderings | 8.2 | 1,620 |
| 7 | Knowledge of Causes, and Secret Motion of Things | 8.6 | 1,693 |
| 8 | Variable and Full of Perturbation | 7.7 | 1,645 |
| 9 | Things Which Have Never Yet Been Done | 8.5 | 1,594 |
| 10 | By Means Which Have Never Yet Been Tried | 9.0 | 1,957 |
8.33 avg 10 episodes 8.1 → 9.0 44 min avg
| # | Title | Rating | Votes |
|---|---|---|---|
| 1 | The Weight of This Combination | 8.1 | 1,631 |
| 2 | Transitory Sacrifices of Crisis | 7.8 | 1,429 |
| 3 | Formalized, Complex, and Costly | 7.9 | 1,371 |
| 4 | Newer Elements of Our Defense | 7.9 | 1,352 |
| 5 | Scarred by Many Past Frustrations | 8.2 | 1,379 |
| 6 | Certain Agony of the Battlefield | 9.1 | 2,159 |
| 7 | Community of Dreadful Fear and Hate | 8.3 | 1,414 |
| 8 | Ruthless in Purpose, and Insidious in Method | 8.5 | 1,387 |
| 9 | Insolvent Phantom of Tomorrow | 8.5 | 1,361 |
| 10 | History Yet to Be Written | 9.0 | 1,622 |
8.42 avg 10 episodes 8.6 → 8.6 44 min avg
| # | Title | Rating | Votes |
|---|---|---|---|
| 1 | The Collapse of Nature | 8.6 | 1,580 |
| 2 | Transgressive Border Crossing | 8.4 | 1,292 |
| 3 | The Stigmata of Progress | 8.1 | 1,199 |
| 4 | From Instinct to Rational Control | 8.2 | 1,191 |
| 5 | Human Raw Material | 8.3 | 1,230 |
| 6 | The Scandal of Altruism | 9.2 | 1,953 |
| 7 | The Antisocialism of Sex | 8.0 | 1,252 |
| 8 | The Redesign of Natural Objects | 8.3 | 1,173 |
| 9 | The Mitigation of Competition | 8.5 | 1,212 |
| 10 | From Dancing Mice to Psychopaths | 8.6 | 1,379 |
8.32 avg 10 episodes 7.8 → 9.1 42 min avg
| # | Title | Rating | Votes |
|---|---|---|---|
| 1 | The Few Who Dare | 7.8 | 1,196 |
| 2 | Clutch of Greed | 8.0 | 1,114 |
| 3 | Beneath Her Heart | 8.0 | 1,091 |
| 4 | Let the Children and Childbearers Toil | 7.6 | 1,068 |
| 5 | Ease for Idle Millionaires | 7.9 | 1,072 |
| 6 | Manacled Slim Wrists | 8.2 | 1,078 |
| 7 | Gag or Throttle | 8.8 | 1,240 |
| 8 | Guillotines Decide | 9.0 | 1,293 |
| 9 | One Fettered Slave | 8.8 | 1,126 |
| 10 | To Right the Wrongs of Many | 9.1 | 1,593 |