Simplify the following text for a Grade 8 native English-speaking person.
Original: Ã -- tzi had several carbon tattoos including groups of short , parallel , vertical lines to both sides of the lumbar spine , a cruciform mark behind the right knee , and various marks around both ankles .
Simplified: The tattoos were carbon ( soot ) . There were groups of short , parallel , vertical lines to both sides of the lumbar spine , a cross-shaped mark behind the right knee , and various marks around both ankles .