C string behaving strangely when longer than 7 characters

I am trying to create a program in C which takes a user's input and 'evolves' a random string until it matches the input. So far it works fine on input which is 7 characters or less, but as soon as a user enters 8 characters the program doesn't work. I can't figure out where I am going wrong. Here's the code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>

void mutate(char ancestor[], char descendent[]);
void evolve(char descendent[]);

int main(void)
{
    srand(time(NULL));
    char input[50];

    printf("Please Enter a String:n");
    scanf("%s", input);

    evolve(input);
    retu 0;


void evolve(char descendent[])
{
    size_t length = strlen(descendent);
    char ancestor[50];
    int i;
    for(i = 0; i < length; i++)
        ancestor[i] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"[rand() % 52];
    while(strcmp(ancestor, descendent)){
        mutate(ancestor, descendent);
        printf("%sn", ancestor);
    }
}

void mutate(char ancestor[], char descendent[])
{
    int i;
    size_t length = strlen(descendent);
    for(i = 0; i < length; i++){
        if(ancestor[i] != descendent[i]){
            ancestor[i] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"[rand() % 52];
        }
    }
}