Messages beta is the App
iMessages are what are sent to iOS devices or someone else's Messages beta.
If you clear messages (small m) before quitting then no messages will show up on restart.
If you leave a chat open there will show up.
The "History" that shows can be iMessage stuff or if you have saved Transcripts from iChat an "iChat Style" chat will pull those Saved Chats as "history".
You may get items on the left if Messages beta has to sync some Off line iMessages that happened on your iPhone of iPad.
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Lion 10.7.4)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.7.4),
"Limit the Logs to the Bits above Binary Images." No, Seriously