For folks in the USA, happy Martin Luther King Jr. Day! This week on Petri Dish Nathan and Sean discuss the biology of aging. What does it actually mean to age, when some animals out there are biologically immortal and get to just hang out forever until they get eaten? What happens on a cellular level when we age? What can we learn from other species about the aging process? This is the first part of a two-part series -- next week we'll discuss human aging in the context of what we can try to do to slow or halt it!References:https://www.pnas.org/content/early/2020/01/07/1916548117https://www.sciencedirect.com/science/article/pii/S0092867413006454https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4247388/https://www.sciencedirect.com/science/article/pii/S2211124714010195https://www.pnas.org/content/early/2019/09/12/1904611116https://en.wikipedia.org/wiki/Nothobranchius_furzerihttps://onlinelibrary.wiley.com/doi/full/10.1111/j.1474-9726.2012.00847.xhttps://link.springer.com/article/10.1007/s11357-013-9597-9https://www.nature.com/articles/ncomms14063https://royalsocietypublishing.org/doi/full/10.1098/rsbl.2010.0539https://onlinelibrary.wiley.com/doi/full/10.1002/bies.201000132https://www.sciencedirect.com/science/article/pii/S1568163714000622https://en.wikipedia.org/wiki/Turritopsis_dohrniihttps://oaktrust.library.tamu.edu/handle/1969.1/173118https://www.sciencedirect.com/science/article/pii/S1055790316303359https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5964061/https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6326690/https://www.sciencedirect.com/science/article/pii/S0047637417300015https://bmcbiol.biomedcentral.com/articles/10.1186/s12915-018-0547-yhttps://www.pnas.org/content/115/8/1801.shorthttps://www.hindawi.com/journals/omcl/2019/4502819/abs/https://www.sciencedirect.com/science/article/pii/B978012411596500006Xhttps://www.sciencedirect.com/science/article/pii/S0092867416309813