Is there an R function for combining two replicate site columns in a table to show presence absence of species?

I have the following DF (example data, my actual data set is 96 columns):

   class   X1A X1B X2A X2B X3A X3B X4A X4B X5A X5B X6A X6B
1       A     0   1   0   0   0   0   0   1   1   1   1   1
2       B     1   1   1   1   0   0   0   1   1   1   0   1
3       C     0   0   0   1   1   0   0   0   1   1   0   0
4       D     0   0   0   1   1   0   1   0   1   0   0   0
5       A     0   1   1   1   0   0   0   1   1   1   1   1
6       B     0   0   1   1   0   0   0   1   1   1   0   1
7       C     0   0   0   1   1   0   0   0   1   1   0   0
8       D     0   0   0   1   1   0   1   0   1   0   0   0
9       A     0   1   1   1   0   0   0   1   1   1   1   1
10      B     1   1   1   1   0   0   0   1   1   1   0   1
11      C     0   0   0   1   1   0   0   0   1   1   0   0
12      D     0   1   0   1   1   0   1   0   1   0   0   0

Class denotes the phylogenic class of the organism (each replicate of the letter is a different species but members of the same class). 1A and 1B are samples from the same site. I want to combine the two presence/absence data (1/0 respectively) from each two samples from every site and add up the number of "presences" for the class across that site. so that my df now looks something like this:

  Sample Class  Number of Species Present  
      1     A     3  
      1     B     2  
      1     C     0  
      1     D     1  
      2     A     2  
      2     B     3  
      2     C     3  
      2     D     3

For example, in the original df you see that Class C species are not present in sample 2A at all but each species of class C is present in sample 2B. So the output df records Species C as present 3 times in sample 2. Furthermore, Class B has 3 different species occur in 2A and in 2B but because they are replicates of the output df records sample 2 as having 3 Class B species present.

Any help would be appreactiated as I'm stumped!

Cheers!!

Read more here: https://stackoverflow.com/questions/67001957/is-there-an-r-function-for-combining-two-replicate-site-columns-in-a-table-to-sh