Muddy footprints suggest 2 species of early humans were neighbors in Kenya 1.5 million years ago The Associated PressFootprints Suggest Different Human Relatives Lived Alongside One Another The New York TimesContemporary hominin locomotor diversity ScienceFootprints reveal the coexistence of two human species 1.5 million years ago EL PAÍS USARare footprints suggest two of our prehistoric ancestors may have met The Washington Post