Was the Vector hierarchy ever Serializable?

I am in the midst of upgrading our Mahout library in order to take
advantage of all the excellent recent additions.

As far as I can tell, the library was based off a snapshot of 0.5. The code
does not use any of the Mahout algorithms, just a few of the data
structures such as DenseVector. The existing code builds a Java object
which is then serialized and distributed. After upgrading to 0.9, I noticed
I was no longer able to deserialize objects since DenseVector is
not Serializable. After inspect the old jar, it seems like AbstractVector
was declared Serializable.

So either someone at my company added serialization to the Mahout classes
or they were Serializable at some point. I am assuming the former. Is this
the case? I looked at the commits and at no point was anything Serializable.

Since the classes are not Serializable and no longer inherit from Writable,
is there an existing strategy to output Mahout structures? Would hate to
write wrapper classes or once again modify the source.

Cheers,

Ivan