This is a planked top table with breadboard ends. The planked boards run perpendicular to the end pieces and the dowels you see are how these 2 large pieces attach with a dado joint.
What you may see over time is Mother Nature working in tandem with your solid wood table. This is dependent on the conditions of your home and the humidity levels that you are experiencing, whether you will see changes in your table.
Even after the tree is cut down the wood will take on and release moisture, which is called expansion or contraction. Breadboard tables were designed for this purpose. The circles that you see cut are expansion and contraction joints hidden below the surface of the wood. Your table can expand up to a 1/8” of an inch throughout the season. Simply put a touch of stain to cover up any exposed unfinished wood.