How to use only serif fonts in whole document?

Question

I'm wondering how to use only serif fonts in whole document. Remark: I use one of the KOMA Script document classes, which employ sans-serif fonts for chapter and sectioning headers.

I've managed to change the table of contents with KOMA, but e.g. setkoma commands won't work for all the headings.

This is my main document:

\input{chapter/header}
\setlength{\unitlength}{1mm}
\makeindex
\makenomenclature

\begin{document}%

\begin{spacing}{1}%Normal Spacing
\renewcommand*{\theHchapter}{0.\arabic{chapter}} %so that no double Chapter I (prob with hyperref)
\pagenumbering{roman}
\setcounter{secnumdepth}{-1} %No number in front of Chapter
\maketitle 

\clearpage
\thispagestyle{empty}
\hfill
\clearpage

\input{chapter/Declaration}

\clearpage
\thispagestyle{empty}
\hfill
\clearpage

\input{chapter/Abstract}

\clearpage
\thispagestyle{empty}
\hfill
\clearpage

\renewcommand*{\theHchapter}{\arabic{chapter}} %so that no double Chapter I (prob with hyperref)
    %TOC etc.
\setcounter{secnumdepth}{4} %Numbers in front of Chapter etc
\setcounter{tocdepth}{4} 
\pagenumbering{Roman}

This is my header.tex:

\documentclass[a4paper,%
                            english,%
                            numbers=noenddot,%not 1.1. but 1.1 (früher: pointlessnumbers)
                            oneside,%
                            bibliography=totoc,%früher: bibtotoc
                            listof=totoc,%früher: liststotoc
                            %draft
]{scrreprt}
\usepackage[pdftex]{graphicx}
\pdfoutput=1
\pdfcompresslevel=9
%\DeclareGraphicsRule{.tif}{bmp}{}{}            %see epslatex.ps
\DeclareGraphicsExtensions{.pdf,.png,.jpg,.mps} %see epslatex.ps
\graphicspath{{bilder/}}
\usepackage[english]{babel}

\usepackage[latin1]{inputenc}%zuständig für umlaute und scharfes s (ß)

Answer 1

To make all the headings "no sans serif" - or for short "serif" - there is a special documentclass option:

\documentclass[egregdoesnotlikesansseriftitles]{scrbook}

\begin{document}
\chapter{test}
test
\end{document}

Update for koma v3.39 or newer

The option now has the boring name sfdefaults=false:

\documentclass[sfdefaults=false]{scrbook}

\begin{document}
\chapter{test}
test
\end{document}