The Same Person Writing in 1830 and 1847?

The image in this blog post is a marriage bond signed by a Thomas Brown and Alexander Riley in 1830 in Bourbon County, Kentucky, and was made from a digital image of the bond which appeared on FamilySearch. 

Yesterday's post included an 1847 marriage bond from Mercer County, Kentucky, signed by John Lake and a Thomas Brown.

The signatures from both bonds have been contrasted in the image shown below:

Are the two signatures the same? It is important to note that any person's signature can easily change over seventeen years and the type of pen being used and the writing surface can impact how different two signatures look--even when it is known that they are from the same person. The "T" in "Thomas" is different. However, the rest of the signatures are very similar (part of the last name is difficult to read in the 1830 signature).

If Thomas Brown was not such a common name this would not quite be the problem that it is.