- Kelly Hunter - Herself - Narrator
- Andrew Scott - Narrator
- Helen McCrory - Narrator
- Rupert Penry-Jones - Himself - Narrator
- Adrian Lester - Himself - Narrator
- Dr Adam Rutherford - Presenter
- Steven Mackintosh - Himself - Narrator
- Hugo Speer - Narrator
- Gabriel Weston - Presenter
- David Harewood - Narrator
- John Hannah - Himself - Narrator
- Peter Gibbs - Self - Presenter
- Giles Yeo - Presenter
- Adam Pearson - Presenter
- Chris van Tulleken - Presenter
- Daniel Kahneman - Presenter
- Toby Macdonald - Presenter
- Uta Frith - Presenter
- Anne Glover - Herself - Presenter
- Dr Zoe Williams - Herself - Presenter
- Xand van Tulleken - Presenter
- Xand van Tulleken - Self - Presenter
- Tim Berners-Lee - Himself - Interviewed Guest
- Laura Waters - Herself - Presenter
- Alice Roberts - Self - Presenter
- Julian Assange - Himself - Interviewed Guest
- Robert Smith - Himself
- Michael Mosley - Self - Presenter
- Michael Mosley - Narrator
- Michael Mosley - Himself
- John Hammond - Self - Presenter
- David Attenborough - Self
- David Attenborough - Himself / Narrator
- Helen Czerski - Self - Presenter
- Iain Stewart - Self - Presenter
- Liz Bonnin - Self - Presenter
- Hannah Fry - Self - Presenter
- Hannah Fry - Self
- Paul McGann - Himself
- Toby Jones - Narrator
- Danny Wallace - Himself
- Fergal Keane - Self - Presenter
- Katherine Parkinson - Narrator
- Chris Packham - Self
- Frank Gillard - Narrator
- Terrence Hardiman - Trofim Lysenko
- Kevin Fong - Self - Presenter
- Kevin Fong - Presenter
- David Swift - Vavilov
- Simon Lack - Zhukovskii
- Richard Ireson - Prezent
- George Cormack - Michurin
- Forbes Collins - Iakovlev
- Richard Beale - Lysenko's father
- Duncan Geddes - Self
- Sean Conroy - Self
- Peter Middleton - Self
- Buckminster Fuller - Self
- Robert Horne - Self
- Aaron Klug - Self
- John Money - Self
- David Reimer - Self
- Dilly Barlow - Narrator
- Ben Carson - Self
- Richard Feynman - Self
- Richard Feynman - Himself
- Zam Baring - Narrator
- Maria Pearson - Self
- David Van Horn - Self
- Larry Zimmerman - Self
- Suzan Harjo - Self
- Richard Jantz - Self
- Sue Savage-Rumbaugh - Self
- Patricia Marks Greenfield - Self
- Duane Rumbaugh - Self
- Sarah Boyson - Self
- David Lutyens - Self - Reporter
- Beatrix Gardner - Self
- Rayna Green - Self
- Dilly Barlow - Narrator
- Dilly Barlow - Narrator (voice)
- Ian Holm - Narrator
- Tim Ingold - Self
- Paul Martin - Self
- David Meltzer - Self
- David Harris - Self
- Abbot Sekaquaptewa - Self
- James Hazeldine - Self
- Thomas A. Edison - Self
- Michael Swann - Narrator (voice)
- Francis Crick - Self
- James Watson - Self
- Vernon Joyner - Narrator (voice)
- John Slack - Narrator (voice)
- Christophe Boesch - Self
- Sarah Boysen - Self
- Frans de Waal - Self
- Jane Goodall - Self
- Martin Muller - Self
- Crickette Sanz - Self
- Robert Sussman - Self
- Michael Tomasell - Self
- Richard Wrangham - Self
- Danny Wallace - Presenter
- Frank Borman - Self
- Dick Gilling - Self - Presenter
- Rosemary Leach - Self - Narrator (voice)
- Paul Vaughan - Narrator (voice)
- Lucian Msamati - Narrator
- Jack Fortune - Narrator (voice)
- Jack Fortune - Narrator
- Bill Paterson - Narrator
- Brian Cox - Presenter
- Brian Cox - Personter
- Bernard Hill - Narrator
- Jemma Redgrave - Narrator (voice)
- Saul Perlmutter - Self - Lawrence Berkeley Lab
- Alex Filippenko - Self - Astronomical Observer
- Robert Kirshner - Self - Astronomical Observer
- Rocky Kolb - Self - Astronomical Theorist
- Michael Turner - Self - Astronomical Theorist
- Adam Riess - Self - University of California, Berkeley
- Stephen Hawking - Himself
- Alex Hearle
- Catherine Gale
- Charles Colville
- Diana Ellis-Hill
- Helen Williamson
- Matthew Dyas
- Robert Eagle
- Andrew Cohen
- Kate O'Sullivan
- Simon Lamb
- David Sington
- John Wiles
- Alex Keefe
- Adrian Malone
- Graham Massey
- Robin Bates
- Liz Tucker
- Matthew Barrett
Kelly Hunter interpreta a Herself - Narrator en la serie.
Andrew Scott interpreta a Narrator en la serie.
Helen McCrory interpreta a Narrator en la serie.
Rupert Penry-Jones interpreta a Himself - Narrator en la serie.
Adrian Lester interpreta a Himself - Narrator en la serie.
Dr Adam Rutherford interpreta a Presenter en la serie.
Steven Mackintosh interpreta a Himself - Narrator en la serie.
Hugo Speer interpreta a Narrator en la serie.
Gabriel Weston interpreta a Presenter en la serie.
David Harewood interpreta a Narrator en la serie.
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